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Man Page for PERLFUNC



NAME
     perlfunc - Perl builtin functions

DESCRIPTION
     The functions in this section can serve as terms in an
     expression.  They fall into two major categories: list
     operators and named unary operators.  These differ in their
     precedence relationship with a following comma.  (See the
     precedence table in the perlop manpage.)  List operators
     take more than one argument, while unary operators can never
     take more than one argument.  Thus, a comma terminates the
     argument of a unary operator, but merely separates the
     arguments of a list operator.  A unary operator generally
     provides a scalar context to its argument, while a list
     operator may provide either scalar and list contexts for its
     arguments.  If it does both, the scalar arguments will be
     first, and the list argument will follow.  (Note that there
     can only ever be one list argument.)  For instance, splice()
     has three scalar arguments followed by a list.

     In the syntax descriptions that follow, list operators that
     expect a list (and provide list context for the elements of
     the list) are shown with LIST as an argument.  Such a list
     may consist of any combination of scalar arguments or list
     values; the list values will be included in the list as if
     each individual element were interpolated at that point in
     the list, forming a longer single-dimensional list value.
     Elements of the LIST should be separated by commas.

     Any function in the list below may be used either with or
     without parentheses around its arguments.  (The syntax
     descriptions omit the parens.)  If you use the parens, the
     simple (but occasionally surprising) rule is this: It LOOKS
     like a function, therefore it IS a function, and precedence
     doesn't matter.  Otherwise it's a list operator or unary
     operator, and precedence does matter.  And whitespace
     between the function and left parenthesis doesn't count--so
     you need to be careful sometimes:

         print 1+2+3;        # Prints 6.
         print(1+2) + 3;     # Prints 3.
         print (1+2)+3;      # Also prints 3!
         print +(1+2)+3;     # Prints 6.
         print ((1+2)+3);    # Prints 6.

     If you run Perl with the -w switch it can warn you about
     this.  For example, the third line above produces:

         print (...) interpreted as function at - line 1.
         Useless  use  of  integer  addition in void context at -
	 line 1.

     For functions that can be used in either a scalar or list
     context, non-abortive failure is generally indicated in a
     scalar context by returning the undefined value, and in a
     list context by returning the null list.

     Remember the following rule:

     +    THERE IS NO GENERAL RULE FOR CONVERTING A LIST INTO A
          SCALAR!

     Each operator and function decides which sort of value it
     would be most appropriate to return in a scalar context.
     Some operators return the length of the list that would have
     been returned in a list context.  Some operators return the
     first value in the list.  Some operators return the last
     value in the list.  Some operators return a count of
     successful operations.  In general, they do what you want,
     unless you want consistency.

     -X FILEHANDLE

     -X EXPR

     -X      A file test, where X is one of the letters listed
             below.  This unary operator takes one argument,
             either a filename or a filehandle, and tests the
             associated file to see if something is true about
             it.  If the argument is omitted, tests $_, except
             for -t, which tests STDIN.  Unless otherwise
             documented, it returns 1 for TRUE and '' for FALSE,
             or the undefined value if the file doesn't exist.
             Despite the funny names, precedence is the same as
             any other named unary operator, and the argument may
             be parenthesized like any other unary operator.  The
             operator may be any of:

                 -r  File is readable by effective uid/gid.
                 -w  File is writable by effective uid/gid.
                 -x  File is executable by effective uid/gid.
                 -o  File is owned by effective uid.

                 -R  File is readable by real uid/gid.
                 -W  File is writable by real uid/gid.
                 -X  File is executable by real uid/gid.
                 -O  File is owned by real uid.

                 -e  File exists.
                 -z  File has zero size.
                 -s  File has non-zero size (returns size).
                 -f  File is a plain file.
                 -d  File is a directory.
                 -l  File is a symbolic link.
                 -p  File is a named pipe (FIFO).
                 -S  File is a socket.
                 -b  File is a block special file.
                 -c  File is a character special file.
                 -t  Filehandle is opened to a tty.

                 -u  File has setuid bit set.
                 -g  File has setgid bit set.
                 -k  File has sticky bit set.

                 -T  File is a text file.
                 -B  File is a binary file (opposite of -T).

                 -M  Age of file in days when script started.
                 -A  Same for access time.
                 -C  Same for inode change time.

             The interpretation of the file permission operators
             -r, -R, -w, -W, -x and -X is based solely on the
             mode  of the file and the uids and gids of the user.
             There may be other reasons you can't actually read,
             write or execute the file.  Also note that, for the
             superuser, -r, -R, -w and -W always return 1, and -x
             and -X return 1 if any execute bit is set in the
             mode.  Scripts run by the superuser may thus need to
             do a stat() in order to determine the actual mode of
             the file, or temporarily set the uid to something
             else.

             Example:

                 while (<>) {
                     chop;
                     next unless -f $_;      # ignore specials
                     ...
                 }

             Note that -s/a/b/ does not do a negated
             substitution.  Saying -exp($foo) still works as
             expected, however--only single letters following a
             minus are interpreted as file tests.

             The -T and -B switches work as follows.  The first
             block or so of the file is examined for odd
             characters such as strange control codes or
             characters with the high bit set.  If too many odd
             characters (>30%) are found, it's a -B file,
             otherwise it's a -T file.  Also, any file containing
             null in the first block is considered a binary file.


             If -T or -B is used on a filehandle, the current
             stdio buffer is examined rather than the first
             block.  Both -T and -B return TRUE on a null file,
             or a file at EOF when testing a filehandle.

             If any of the file tests (or either the stat() or
             lstat() operators) are given the special filehandle
             consisting of a solitary underline, then the stat
             structure of the previous file test (or stat
             operator) is used, saving a system call.  (This
             doesn't work with -t, and you need to remember that
             lstat() and -l will leave values in the stat
             structure for the symbolic link, not the real file.)
             Example:

                 print "Can do.0 if -r $a || -w _ || -x _;

                 stat($filename);
                 print "Readable0 if -r _;
                 print "Writable0 if -w _;
                 print "Executable0 if -x _;
                 print "Setuid0 if -u _;
                 print "Setgid0 if -g _;
                 print "Sticky0 if -k _;
                 print "Text0 if -T _;
                 print "Binary0 if -B _;


     abs VALUE
             Returns the absolute value of its argument.

     accept NEWSOCKET,GENERICSOCKET
             Accepts an incoming socket connect, just as the
             accept(2) system call does.  Returns the packed
             address if it succeeded, FALSE otherwise.  See
             example in the perlipc manpage.

     alarm SECONDS
             Arranges to have a SIGALRM delivered to this process
             after  the specified number of seconds have elapsed.
             (On some machines, unfortunately, the elapsed time
             may be up to one second less than you specified
             because of how seconds are counted.)  Only one timer
             may be counting at once.  Each call disables the
             previous timer, and an argument of 0 may be supplied
             to cancel the previous timer without starting a new
             one.  The returned value is the amount of time
             remaining on the previous timer.

             For sleeps of finer granularity than one second, you
             may use Perl's syscall() interface to access
             setitimer(2) if your system supports it, or else see
             the select() entry elsewhere in this  documentbelow.

     atan2 Y,X
             Returns the arctangent of Y/X in the range - to .

     bind SOCKET,NAME
             Binds a network address to a socket, just as the
             bind system call does.  Returns TRUE if it
             succeeded, FALSE otherwise.  NAME should be a packed
             address of the appropriate type for the socket.  See
             example in the perlipc manpage.

     binmode FILEHANDLE
             Arranges for the file to be read or written in
             "binary" mode in operating systems that distinguish
             between binary and text files.  Files that are not
             in binary mode have CR LF sequences translated to LF
             on input and LF translated to CR LF on output.
             Binmode has no effect under Unix; in DOS, it may be
             imperative.  If FILEHANDLE is an expression, the
             value is taken as the name of the filehandle.

     bless REF,PACKAGE

     bless REF
             This function tells the referenced object (passed as
             REF) that it is now an object in PACKAGE--or the
             current package if no PACKAGE is specified, which is
             the usual case.  It returns the reference for
             convenience, since a bless() is often the last thing
             in a constructor.  See the perlobj manpage for more
             about the blessing (and blessings) of objects.

     caller EXPR

     caller   Returns the context of the current subroutine call.
             In a scalar context, returns TRUE if there is a
             caller, that is, if we're in a subroutine or eval()
             or require(), and FALSE otherwise.  In a list
             context, returns

                 ($package,$filename,$line) = caller;

             With EXPR, it returns some extra information that
             the debugger uses to print a stack trace.  The value
             of EXPR indicates how many call frames to go back
             before the current one.

     chdir EXPR
             Changes  the working directory to EXPR, if possible.
             If EXPR is omitted, changes to home directory.
             Returns TRUE upon success, FALSE otherwise.  See
             example under die().

     chmod LIST
             Changes the permissions of a list of files.  The
             first element of the list must be the numerical
             mode.  Returns the number of files successfully
             changed.

                 $cnt = chmod 0755, 'foo', 'bar';
                 chmod 0755, @executables;


     chomp VARIABLE

     chomp LIST

     chomp   This is a slightly safer version of chop (see
             below).  It removes any line ending that corresponds
             to the current value of $/ (also known as
             $INPUT_RECORD_SEPARATOR in the English module).  It
             returns the number of characters removed.  It's
             often used to remove the newline from the end of an
             input record when you're worried that the final
             record may be missing its newline.  When in
             paragraph mode ($/ = ""), it removes all trailing
             newlines from the string.  If VARIABLE is omitted,
             it chomps $_.  Example:

                 while (<>) {
                     chomp;  # avoid on last field
                     @array = split(/:/);
                     ...
                 }

             You can actually chomp anything that's an lvalue,
             including an assignment:

                 chomp($cwd = `pwd`);
                 chomp($answer = <STDIN>);

             If you chomp a list, each element is chomped, and
             the  total number of characters removed is returned.

     chop VARIABLE

     chop LIST

     chop    Chops off the last character of a string and returns
             the character chopped.  It's used primarily to
             remove the newline from the end of an input record,
             but is much more efficient than s/0/ because it
             neither scans nor copies the string.  If VARIABLE is


             omitted, chops $_.  Example:

                 while (<>) {
                     chop;   # avoid on last field
                     @array = split(/:/);
                     ...
                 }

             You can actually chop anything that's an lvalue,
             including an assignment:

                 chop($cwd = `pwd`);
                 chop($answer = <STDIN>);

             If you chop a list, each element is chopped.  Only
             the value of the last chop is returned.

     chown LIST
             Changes the owner (and group) of a list of files.
             The first two elements of the list must be the
             NUMERICAL uid and gid, in that order.  Returns the
             number of files successfully changed.

                 $cnt = chown $uid, $gid, 'foo', 'bar';
                 chown $uid, $gid, @filenames;

             Here's an example that looks up non-numeric uids in
             the passwd file:

                 print "User: ";
                 chop($user = <STDIN>);
                 print "Files: "
                 chop($pattern = <STDIN>);

                 ($login,$pass,$uid,$gid) = getpwnam($user)
                     or die "$user not in passwd file";

                 @ary = <${pattern}>;        # expand filenames
                 chown $uid, $gid, @ary;


     chr NUMBER
             Returns the character represented by that NUMBER in
             the character set.  For example, chr(65) is "A" in
             ASCII.

     chroot FILENAME
             Does the same as the system call of that name.  If
             you don't know what it does, don't worry about it.
             If FILENAME is omitted, does chroot to $_.

     close FILEHANDLE
             Closes the file or pipe associated with the file
             handle, returning TRUE only if stdio successfully
             flushes buffers and closes the system file
             descriptor.  You don't have to close FILEHANDLE if
             you are immediately going to do another open on it,
             since open will close it for you.  (See open().)
             However, an explicit close on an input file resets
             the line counter ($.), while the implicit close done
             by open() does not.  Also, closing a pipe will wait
             for the process executing on the pipe to complete,
             in case you want to look at the output of the pipe
             afterwards.  Closing a pipe explicitly also puts the
             status value of the command into $?.  Example:

                 open(OUTPUT, '|sort >foo'); # pipe to sort
                 ...                            # print stuff to output
                 close  OUTPUT;                 # wait for sort to finish
                 open(INPUT, 'foo');            # get sort's results

             FILEHANDLE may be an expression whose value gives
             the real filehandle name.

     closedir DIRHANDLE
             Closes a directory opened by opendir().

     connect SOCKET,NAME
             Attempts to connect to a remote socket, just as the
             connect system call does.  Returns TRUE if it
             succeeded, FALSE otherwise.  NAME should be a
             package address of the appropriate type for the
             socket.  See example in the perlipc manpage.

     cos EXPR
             Returns the cosine of EXPR (expressed in radians).
             If EXPR is omitted takes cosine of $_.

     crypt PLAINTEXT,SALT
             Encrypts a string exactly like the crypt(3) function
             in the C library.  Useful for checking the password
             file for lousy passwords, amongst other things.
             Only the guys wearing white hats should do this.

             Here's an example that makes sure that whoever runs
             this program knows their own password:

                 $pwd = (getpwuid($<))[1];
                 $salt = substr($pwd, 0, 2);
                 system "stty -echo";
                 print "Password: ";
                 chop($word = <STDIN>);
                 print "0;
                 system "stty echo";

                 if (crypt($word, $salt) ne $pwd) {
                     die "Sorry...0;
                 } else {
                     print "ok0;
                 }

             Of course, typing in your own password to whoever
             asks you for it is unwise at best.

     dbmclose ASSOC_ARRAY
             [This function has been superseded by the untie()
             function.]

             Breaks the binding between a DBM file and an
             associative array.

     dbmopen ASSOC,DBNAME,MODE
             [This function has been superseded by the tie()
             function.]

             This binds a dbm(3) or ndbm(3) file to an
             associative array.  ASSOC is the name of the
             associative array.  (Unlike normal open, the first
             argument is NOT a filehandle, even though it looks
             like one).  DBNAME is the name of the database
             (without the .dir or .pag extension).  If the
             database does not exist, it is created with
             protection specified by MODE (as modified by the
             umask()).  If your system only supports the older
             DBM functions, you may perform only one dbmopen() in
             your program.  If your system has neither DBM nor
             ndbm, calling dbmopen() produces a fatal error.

             If you don't have write access to the DBM file, you
             can only read associative array variables, not set
             them.  If you want to test whether you can write,
             either use file tests or try setting a dummy array
             entry inside an eval(), which will trap the error.

             Note that functions such as keys() and values() may
             return huge array values when used on large DBM
             files.  You may prefer to use the each() function to
             iterate over large DBM files.  Example:

                 # print out history file offsets
                 dbmopen(%HIST,'/usr/lib/news/history',0666);
                 while (($key,$val) = each %HIST) {
                     print $key, ' = ', unpack('L',$val), "0;
                 }
                 dbmclose(%HIST);


     defined EXPR
             Returns a boolean value saying whether the lvalue
             EXPR has a real value or not.  Many operations
             return the undefined value under exceptional
             conditions, such as end of file, uninitialized
             variable, system error and such.  This function
             allows you to distinguish between an undefined null
             scalar and a defined null scalar with operations
             that might return a real null string, such as
             referencing elements of an array.  You may also
             check to see if arrays or subroutines exist.  Use of
             defined on predefined variables is not guaranteed to
             produce intuitive results.

             When used on a hash array element, it tells you
             whether the value is defined, not whether the key
             exists in the hash.  Use exists() for that.

             Examples:

                 print if defined $switch{'D'};
                 print "$val0 while defined($val = pop(@ary));
                 die "Can't readlink $sym: $!"
                     unless defined($value = readlink $sym);
                 eval '@foo = ()' if defined(@foo);
                 die "No XYZ package defined" unless defined %_XYZ;
                 sub foo { defined &$bar ? &$bar(@_) : die "No bar"; }

             See also undef().

     delete EXPR
             Deletes the specified value from its hash array.
             Returns the deleted value, or the undefined value if
             nothing was deleted.  Deleting from $ENV{} modifies
             the environment.  Deleting from an array tied to a
             DBM file deletes the entry from the DBM file.  (But
             deleting from a tie()d hash doesn't necessarily
             return anything.)

             The following deletes all the values of an

                 foreach $key (keys %ARRAY) {
                     delete $ARRAY{$key};
                 }

             (But it would be faster to use the undef() command.)
             Note that the EXPR can be arbitrarily complicated as
             long as the final operation is a hash key lookup:

                 delete $ref->[$x][$y]{$key};


     die LIST
             Outside of an eval(), prints the value of LIST to
             STDERR and exits with the current value of $!
             (errno).  If $! is 0, exits with the value of ($? >>
             8) (`command` status).  If ($? >> 8) is 0, exits
             with 255.  Inside an eval(), the error message is
             stuffed into $@.  and the eval() is terminated with
             the undefined value.

             Equivalent examples:

                 die "Can't cd to spool: $!\n" unless chdir '/usr/spool/news';
                 chdir '/usr/spool/news' or die "Can't cd to spool: $!\n"

             If the value of EXPR does not end in a newline, the
             current script line number and input line number (if
             any) are also printed, and a newline is supplied.
             Hint: sometimes appending ", stopped" to your
             message will cause it to make better sense when the
             string "at foo line 123" is appended.  Suppose you
             are running script "canasta".

                 die "/etc/games is no good";
                 die "/etc/games is no good, stopped";

             produce, respectively

                 /etc/games is no good at canasta line 123.
                 /etc/games is no good, stopped at canasta line 123.

             See also exit() and warn().

     do BLOCK
             Not really a function.  Returns the value of the
             last command in the sequence of commands indicated
             by BLOCK.  When modified by a loop modifier,
             executes the BLOCK once before testing the loop
             condition.  (On other statements the loop modifiers
             test the conditional first.)
  
     do SUBROUTINE(LIST)
             A deprecated form of subroutine call.  See the
             perlsub manpage.

     do EXPR Uses the value of EXPR as a filename and executes
             the contents of the file as a Perl script.  Its
             primary use is to include subroutines from a Perl
             subroutine library.

                 do 'stat.pl';

             is just like

                 eval `cat stat.pl`;

             except that it's more efficient, more concise, keeps
             track of the current filename for error messages,
             and searches all the -I libraries if the file isn't
             in the current directory (see also the @INC array in
             the section on Predefined Names in the perlvar
             manpage).  It's the same, however, in that it does
             reparse the file every time you call it, so you
             probably don't want to do this inside a loop.

             Note that inclusion of library modules is better
             done with the use() and require() operators.

     dump LABEL
             This causes an immediate core dump.  Primarily this
             is so that you can use the undump program to turn
             your core dump into an executable binary after
             having initialized all your variables at the
             beginning of the program.  When the new binary is
             executed it will begin by executing a goto LABEL
             (with all the restrictions that goto suffers).
             Think of it as a goto with an intervening core dump
             and reincarnation.  If LABEL is omitted, restarts
             the program from the top.  WARNING: any files opened
             at the time of the dump will NOT be open any more
             when the program is reincarnated, with possible
             resulting confusion on the part of Perl.  See also
             -u option in the perlrun manpage.

             Example:
                 #!/usr/bin/perl
                 require 'getopt.pl';
                 require 'stat.pl';
                 %days = (
                     'Sun' => 1,
                     'Mon' => 2,
                     'Tue' => 3,
                     'Wed' => 4,
                     'Thu' => 5,
                     'Fri' => 6,
                     'Sat' => 7,
                 );

                 dump QUICKSTART if $ARGV[0] eq '-d';

                 QUICKSTART:
                 Getopt('f');


     each ASSOC_ARRAY
             Returns a 2 element array consisting of the key and
             value for the next value of an associative array, so
             that you can iterate over it.  Entries are returned
             in an apparently random order.  When the array is
             entirely read, a null array is returned (which when
             assigned produces a FALSE (0) value).  The next call
             to each() after that will start iterating again.
             The iterator can be reset only by reading all the
             elements from the array.  You should not add
             elements to an array while you're iterating over it.
             There is a single iterator for each associative
             array, shared by all each(), keys() and values()
             function calls in the program.  The following prints
             out your environment like the printenv(1) program,
             only in a different order:

                 while (($key,$value) = each %ENV) {
                     print "$key=$value0;
                 }

             See also keys() and values().

     eof FILEHANDLE

     eof     Returns 1 if the next read on FILEHANDLE will return
             end of file, or if FILEHANDLE is not open.
             FILEHANDLE may be an expression whose value gives
             the real filehandle name.  (Note that this function
             actually reads a character and then ungetc()s it, so
             it is not very useful in an interactive context.)
             An eof without an argument returns the eof status
             for the last file read.  Empty parentheses () may be
             used to indicate the pseudo file formed of the files
             listed on the command line, i.e.  eof() is
             reasonable to use inside a while (<>) loop to detect
             the end of only the last file.  Use eof(ARGV) or eof
             without the parentheses to test EACH file in a while
             (<>) loop.  Examples:

                 # insert dashes just before last line of last file
                 while (<>) {
                     if (eof()) {
                         print "--------------0;
                     }
                     print;
                 }

                 # reset line numbering on each input file
                 while (<>) {
                     print "$.$_";
                     if (eof) {      # Not eof().
                         close(ARGV);
                     }
                 }

             Practical hint: you almost never need to use eof in
             Perl, because the input operators return undef when
             they run out of data.

     eval EXPR

     eval BLOCK
             EXPR is parsed and executed as if it were a little
             Perl program.  It is executed in the context of the
             current Perl program, so that any variable settings,
             subroutine or format definitions remain  afterwards.
             The value returned is the value of the last
             expression evaluated, or a return statement may be
             used, just as with subroutines.

             If there is a syntax error or runtime error, or a
             die() statement is executed, an undefined value is
             returned by eval(), and $@ is set to the error
             message.  If there was no error, $@ is guaranteed to
             be a null string.  If EXPR is omitted, evaluates $_.
             The final semicolon, if any, may be omitted from the
	     expression.

             Note that, since eval() traps otherwise-fatal
             errors, it is useful for determining whether a
             particular feature (such as dbmopen() or symlink())
             is implemented.  It is also Perl's exception
             trapping mechanism, where the die operator is used
             to raise exceptions.

             If the code to be executed doesn't vary, you may use
             the eval-BLOCK form to trap run-time errors without
             incurring the penalty of recompiling each time.  The
             error, if any, is still returned in $@.  Examples:

                 # make divide-by-zero non-fatal
                 eval { $answer = $a / $b; }; warn $@ if $@;

                 # same thing, but less efficient
                 eval '$answer = $a / $b'; warn $@ if $@;

                 # a compile-time error
                 eval { $answer = };

                 # a run-time error
                 eval '$answer =';   # sets $@

             With an eval(), you should be especially careful to
             remember what's being looked at when:

                 eval $x;            # CASE 1
                 eval "$x";          # CASE 2

                 eval '$x';          # CASE 3
                 eval { $x };        # CASE 4

                 eval "x++"          # CASE 5
                 $$x++;              # CASE 6

             Cases 1 and 2 above behave identically: they run the
             code contained in the variable $x.  (Although case 2
             has misleading double quotes making the reader
             wonder what else might be happening (nothing is).)
             Cases 3 and 4 likewise behave in the same way: they
             run the code <$x>, which does nothing at all.  (Case
             4 is preferred for purely visual reasons.) Case 5 is
             a place where normally you WOULD like to use double
             quotes, except that in particular situation, you can
             just  use symbolic references instead, as in case 6.

     exec LIST
             The exec() function executes a system command AND
             NEVER RETURNS.  Use the system() function if you
             want it to return.

             If there is more than one argument in LIST, or if
             LIST is an array with more than one value, calls
             execvp(3) with the arguments in LIST.  If there is
             only one scalar argument, the argument is checked
             for shell metacharacters.  If there are any, the
             entire argument is passed to /bin/sh -c for parsing.
             If there are none, the argument is split into words
             and passed directly to execvp(), which is more
             efficient.  Note: exec() (and system(0) do not flush
             your output buffer, so you may need to set $| to
             avoid lost output.  Examples:

                 exec '/bin/echo', 'Your arguments are: ', @ARGV;
                 exec "sort $outfile | uniq";

             If you don't really want to execute the first
             argument, but want to lie to the program you are
             executing about its own name, you can specify the
             program you actually want to run as an "indirect
             object" (without a comma) in front of the LIST.
             (This always forces interpretation of the LIST as a
             multi-valued list, even if there is only a single
             scalar in the list.)  Example:

                 $shell = '/bin/csh';
                 exec $shel  '-sh';        # pretend it's a login shell

             or, more directly,

                 exec {'/bin/csh'} '-sh';  # pretend it's a login shell


     exists EXPR
             Returns TRUE if the specified hash key exists in its
             hash array, even if the corresponding value is
             undefined.

                 print "Exists0 if exists $array{$key};
                 print "Defined0 if defined $array{$key};
                 print "True0 if $array{$key};

             A hash element can only be TRUE if it's defined, and
             defined if it exists, but the reverse doesn't
             necessarily hold true.

             Note that the EXPR can be arbitrarily complicated as
             long as the final operation is a hash key lookup:

                 if (exists $ref->[$x][$y]{$key}) { ... }

     exit EXPR
             Evaluates EXPR and exits immediately with that
             value.  (Actually, it calls any defined END routines
             first, but the END routines may not abort the exit.
             Likewise any object destructors that need to be
             called are called before exit.)  Example:
  
                 $ans = <STDIN>;
                 exit 0 if $ans =~ /^[Xx]/;

             See also die().  If EXPR is omitted, exits with 0
             status.

     exp EXPR
             Returns e (the natural logarithm base) to the power
             of EXPR. If EXPR is omitted, gives exp($_).

     fcntl FILEHANDLE,FUNCTION,SCALAR
             Implements the fcntl(2) function.  You'll probably
             have to say

                 use Fcntl;

             first to get the correct function definitions.
             Argument processing and value return works just like
             ioctl() below.  Note that fcntl() will produce a
             fatal error if used on a machine that doesn't
             implement fcntl(2).  For example:

                 use Fcntl;
                 fcntl($filehandle, F_GETLK, $packed_return_buffer);


     fileno FILEHANDLE
             Returns the file descriptor for a filehandle.  This
             is useful for constructing bitmaps for select().  If
             FILEHANDLE is an expression, the value is taken as
             the name of the filehandle.

     flock FILEHANDLE,OPERATION
             Calls flock(2) on FILEHANDLE.  See the flock(2)
             manpage for definition of OPERATION.  Returns TRUE
             for success, FALSE on failure.  Will produce a fatal
             error if used on a machine that doesn't implement
             flock(2).  Here's a mailbox appender for BSD
             systems.

                 $LOCK_SH = 1;
	         $LOCK_EX = 2;
		 $LOCK_NB = 4;
		 $LOCK_UN = 8;
		 
                 sub unlock {
                     flock(MBOX,$LOCK_UN);
		     # and, in case someone appended
		     # while we were waiting...
		     seek(MBOX, 0, 2);
                 }
                 sub unlock {
                     flock(MBOX,$LOCK_UN);
                 }
  
                 open(MBOX, ">>/usr/spool/mail/$ENV{'USER'}")
                         or die "Can't open mailbox: $!";

                 lock();
                 print MBOX $msg,"\n\n";
                 unlock();

             Note that flock() can't lock things over the
             network.  You need to do locking with fcntl() for
             that.

     fork    Does a fork(2) system call.  Returns the child pid
             to the parent process and 0 to the child process, or
             undef if the fork is unsuccessful.  Note: unflushed
             buffers remain unflushed in both processes, which
             means you may need to set $| ($AUTOFLUSH in English)
             or call the autoflush() FileHandle method to avoid
             duplicate output.

             If you fork() without ever waiting on your children,
             you will accumulate zombies:

                 $SIG{'CHLD'} = sub { wait };

             There's also the double-fork trick (error checking
             on fork() returns omitted);

                 unless ($pid = fork) {
                     unless (fork) {
                         exec "what you really wanna do";
                         die "no exec";
                         # ... or ...
                         some_perl_code_here;
                         exit 0;
                     }
                     exit 0;
                 }
		 waitpid($pid,0);

     formline PICTURE, LIST
             This is an internal function used by formats, though
             you may call it too.  It formats (see the perlform
             manpage) a list of values according to the contents
             of PICTURE, placing the output into the format
             output accumulator, $^A.  Eventually, when a write()
             is done, the contents of $^A are written to some
             filehandle, but you could also read $^A yourself and
             then set $^A back to "".  Note that a format
             typically does one formline() per line of form, but
             the formline() function itself doesn't care how many
             newlines are embedded in the PICTURE.  Be careful if
             you put double quotes around the picture, since an
             "@" character may be taken to mean the beginning of
             an array name.  formline() always returns TRUE.

     getc FILEHANDLE

     getc    Returns the next character from the input file
             attached to FILEHANDLE, or a null string at end of
             file.  If FILEHANDLE is omitted, reads from STDIN.

     getlogin
             Returns the current login from /etc/utmp, if any.
             If null, use getpwuid().

                 $login = getlogin || (getpwuid($<))[0] ||  "Kilroy";


     getpeername SOCKET
             Returns the packed sockaddr address of other end of
             the SOCKET connection.

                 # An internet sockaddr
                 $sockaddr = 'S n a4 x8';
                 $hersockaddr = getpeername(S);
                 ($family, $port, $heraddr) = unpack($sockaddr,$hersockaddr);


     getpgrp PID
             Returns the current process group for the specified
             PID, 0 for the current process.  Will produce a
             fatal error if used on a machine that doesn't
             implement getpgrp(2).  If PID is omitted, returns
             process group of current process.

     getppid Returns the process id of the parent process.
  
     getpriority WHICH,WHO
             Returns the current priority for a process, a
             process group, or a user.  (See the getpriority(2)
             manpage.)  Will produce a fatal error if used on a
             machine that doesn't implement getpriority(2).
  
     getpwnam NAME
   
     getgrnam NAME
 
     gethostbyname NAME

     getnetbyname NAME

     getprotobyname NAME

     getpwuid UID

     getgrgid GID

     getservbyname NAME,PROTO

     gethostbyaddr ADDR,ADDRTYPE

     getnetbyaddr ADDR,ADDRTYPE

     getprotobynumber NUMBER

     getservbyport PORT,PROTO

     getpwent

     getgrent

     gethostent

     getnetent

     getprotoent

     getservent

     setpwent

     setgrent

     sethostent STAYOPEN

     setnetent STAYOPEN

     setprotoent STAYOPEN
 
     setservent STAYOPEN
  
     endpwent
  
     endgrent
 
     endhostent
 
     endnetent
  
     endprotoent

     endservent
             These routines perform the same functions as their
             counterparts in the system library.  Within a list
             context, the return values from the various get
             routines are as follows:

                 ($name,$passwd,$uid,$gid,
                    $quota,$comment,$gcos,$dir,$shell) = getpw*
                 ($name,$passwd,$gid,$members) = getgr*
                 ($name,$aliases,$addrtype,$length,@addrs) = gethost*
                 ($name,$aliases,$addrtype,$net) = getnet*
                 ($name,$aliases,$proto) = getproto*
                 ($name,$aliases,$port,$proto) = getserv*

             (If the entry doesn't exist you get a null list.)

             Within a scalar context, you get the name, unless
             the function was a lookup by name, in which case you
             get the other thing, whatever it is.  (If the entry
             doesn't exist you get the undefined value.)  For
             example:

                 $uid = getpwnam
                 $name = getpwuid
                 $name = getpwent
                 $gid = getgrnam
                 $name = getgrgid
                 $name = getgrent
                 etc.

             The $members value returned by getgr*() is a space
             separated list of the login names of the members of
             the group.

             For the gethost*() functions, if the h_errno
             variable is supported in C, it will be returned to
             you via $? if the function call fails.  The @addrs
             value returned by a successful call is a list of the
             raw addresses returned by the corresponding system
             library call.  In the Internet domain, each address
             is four bytes long and you can unpack it by saying
             something like:
 
                 ($a,$b,$c,$d) = unpack('C4',$addr[0]);
 
     getsockname SOCKET
             Returns the packed sockaddr address of this end of
             the SOCKET connection.

                 # An internet sockaddr
                 $sockaddr = 'S n a4 x8';
                 $mysockaddr = getsockname(S);
                 ($family, $port, $myaddr) =
                                 unpack($sockaddr,$mysockaddr);


     getsockopt SOCKET,LEVEL,OPTNAME
             Returns the socket option requested, or undefined if
             there is an error.

     glob EXPR
             Returns the value of EXPR with filename expansions
             such as a shell would do.  This is the internal
             function implementing the <*.*> operator.

     gmtime EXPR
             Converts a time as returned by the time function to
             a 9-element array with the time analyzed for the
             Greenwich timezone.  Typically used as follows:

                 ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) =
                                                         gmtime(time);

             All array elements are numeric, and come straight
             out of a struct tm.  In particular this means that
             $mon has the range 0..11 and $wday has the range
             0..6.  If EXPR is omitted, does gmtime(time()).

     goto LABEL

     goto &NAME
             The goto-LABEL form finds the statement labeled with
             LABEL and resumes execution there.  It may not be
             used to go into any construct that requires
             initialization, such as a subroutine or a foreach
             loop.  It also can't be used to go into a construct
             that is optimized away.  It can be used to go almost
             anywhere else within the dynamic scope, including
             out of subroutines, but it's usually better to use
             some other construct such as last or die.  The
             author of Perl has never felt the need to use this
             form of goto (in Perl, that is--C is another
             matter).
  
             The goto-&NAME form is highly magical, and
             substitutes a call to the named subroutine for the
             currently running subroutine.  This is used by
             AUTOLOAD subroutines that wish to load another
             subroutine and then pretend that the other
             subroutine had been called in the first place
             (except that any modifications to @_ in the current
             subroutine are propagated to the other  subroutine.)
             After the goto, not even caller() will be able to
             tell that this routine was called first.

     grep BLOCK LIST

     grep EXPR,LIST
             Evaluates the BLOCK or EXPR for each element of LIST
             (locally setting $_ to each element) and returns the
             list value consisting of those elements for which
             the expression evaluated to TRUE.  In a scalar
             context, returns the number of times the expression
             was TRUE.

                 @foo = grep(!/^#/, @bar);    # weed out comments

             or equivalently,

                 @foo = grep {!/^#/} @bar;    # weed out comments

             Note that, since $_ is a reference into the list
             value, it can be used to modify the elements of the
             array.  While this is useful and supported, it can
             cause bizarre results if the LIST is not a named
             array.

     hex EXPR
             Returns the decimal value of EXPR interpreted as an
             hex string.  (To interpret strings that might start
             with 0 or 0x see oct().)  If EXPR is omitted, uses
             $_.

     import  There is no built-in import() function.  It is
             merely an ordinary method subroutine defined (or
             inherited) by modules that wish to export names to
             another module.  The use() function calls the
	     import() method for the package used.  See also the
             use entry elsewhere in this documentbelow and the
             perlmod manpage.

     index STR,SUBSTR,POSITION
  
     index STR,SUBSTR
             Returns the position of the first occurrence of
             SUBSTR in STR at or after POSITION.  If POSITION is
             omitted, starts searching from the beginning of the
             string.  The return value is based at 0, or whatever
             you've set the $[ variable to.  If the substring is
             not found, returns one less than the base,
             ordinarily -1.

     int EXPR
             Returns the integer portion of EXPR.  If EXPR is
             omitted, uses $_.

     ioctl FILEHANDLE,FUNCTION,SCALAR
             Implements the ioctl(2) function.  You'll probably
             have to say

                 require "ioctl.ph"; # probably /usr/local/lib/perl/ioctl.ph

             first to get the correct function definitions.  If
             ioctl.ph doesn't exist or doesn't have the correct
             definitions you'll have to roll your own, based on
             your C header files such as <sys/ioctl.h>.  (There
             is a Perl script called h2ph that comes with the
             Perl kit which may help you in this.)  SCALAR will
             be read and/or written depending on the FUNCTION--a
             pointer to the string value of SCALAR will be passed
             as the third argument of the actual ioctl call.  (If
             SCALAR has no string value but does have a numeric
             value, that value will be passed rather than a
             pointer to the string value.  To guarantee this to
             be TRUE, add a 0 to the scalar before using it.)
             The pack() and unpack() functions are useful for
             manipulating the values of structures used by
             ioctl().  The following example sets the erase
             character to DEL.

                 require 'ioctl.ph';
                 $sgttyb_t = "ccccs";         # 4 chars and a short
                 if (ioctl(STDIN,$TIOCGETP,$sgttyb)) {
                     @ary = unpack($sgttyb_t,$sgttyb);
                     $ary[2] = 127;
                     $sgttyb = pack($sgttyb_t,@ary);
                     ioctl(STDIN,$TIOCSETP,$sgttyb)
                         || die "Can't ioctl: $!";
		 }
  
             The return value of ioctl (and fcntl) is as follows:
 
                     if OS returns:          then Perl returns:
                         -1                    undefined value
                          0                  string "0 but true"
                     anything else               that number
  
             Thus Perl returns TRUE on success and FALSE on
             failure, yet you can still easily determine the
             actual value returned by the operating system:

                 ($retval = ioctl(...)) || ($retval = -1);
                 printf "System returned %d0, $retval;

     join EXPR,LIST
             Joins the separate strings of LIST or ARRAY into a
             single string with fields separated by the value of
             EXPR, and returns the string.  Example:

                 $_ = join(':',$login,$passwd,$uid,$gid,$gcos,$home,$shell);

             See the split entry in the perlfunc manpage.

     keys ASSOC_ARRAY
             Returns a normal array consisting of all the keys of
             the named associative array.  (In a scalar context,
             returns the number of keys.) The keys are returned
             in an apparently random order, but it is the same
             order as either the values() or each() function
             produces (given that the associative array has not
             been modified).  Here is yet another way to print
             your environment:

                 @keys = keys %ENV;
                 @values = values %ENV;
                 while ($#keys >= 0) {
                     print pop(@keys), '=', pop(@values), "0;
                 }

             or how about sorted by key:

                 foreach $key (sort(keys %ENV)) {
                     print $key, '=', $ENV{$key}, "0;
                 }


     kill LIST
             Sends a signal to a list of processes.  The first
             element of the list must be the signal to send.
             Returns the number of processes successfully
             signaled.
  
                 $cnt = kill 1, $child1, $child2;
                 kill 9, @goners;
  
             Unlike in the shell, in Perl if the SIGNAL is
             negative, it kills process groups instead of
             processes.  (On System V, a negative PROCESS number
             will also kill process groups, but that's not
             portable.)  That means you usually want to use
             positive not negative signals.  You may also use a
             signal name in quotes.

     last LABEL

     last    The last command is like the break statement in C
             (as used in loops); it immediately exits the loop in
             question.  If the LABEL is omitted, the command
             refers to the innermost enclosing loop.  The
             continue block, if any, is not executed:

                 line: while (<STDIN>) {
                     last line if /^$/;       # exit when done with header
                     ...
                 }


     lc EXPR Returns an lowercased version of EXPR.  This is the
             internal function implementing the escape in
             double-quoted strings.

     lcfirst EXPR
             Returns the value of EXPR with the first character
             lowercased.  This is the internal function
             implementing the \l escape in double-quoted strings.

     length EXPR
             Returns the length in characters of the value of
             EXPR.  If EXPR is omitted, returns length of $_.

     link OLDFILE,NEWFILE
             Creates a new filename linked to the old filename.
             Returns 1 for success, 0 otherwise.

     listen SOCKET,QUEUESIZE
             Does the same thing that the listen system call
             does.  Returns TRUE if it succeeded, FALSE
             otherwise.  See example in the perlipc manpage.

     local EXPR
             In general, you should be using "my" instead of
             "local", because it's faster and safer.  Format
             variables have to use "local" though, as do any
             other variables whose local value must be visible to
             called subroutines.  This is known as dynamic
             scoping.  Lexical scoping is done with "my", which
             works more like C's auto declarations.
 
             A local modifies the listed variables to be local to
             the enclosing block, subroutine, eval or "do".  If
             more than one value is listed, the list must be
             placed in parens.  All the listed elements must be
             legal lvalues.  This operator works by saving the
             current values of those variables in LIST on a
             hidden stack and restoring them upon exiting the
             block, subroutine or eval.  This means that called
             subroutines can also reference the local variable,
             but not the global one.  The LIST may be assigned to
             if desired, which allows you to initialize your
             local variables.  (If no initializer is given for a
             particular variable, it is created with an undefined
             value.)  Commonly this is used to name the
             parameters to a subroutine.  Examples:

                 sub RANGEVAL {
                     local($min, $max, $thunk) = @_;
                     local $result = '';
                     local $i;

                     # Presumably $thunk makes reference to $i

                     for ($i = $min; $i < $max; $i++) {
                         $result .= eval $thunk;
                     }

                     $result;
                 }

                 if ($sw eq '-v') {
                     # init local array with global array
                     local @ARGV = @ARGV;
                     unshift(@ARGV,'echo');
                     system @ARGV;
                 }
                 # @ARGV restored

                 # temporarily add to digits associative array
                 if ($base12) {
                     # (NOTE: not claiming this is efficient!)
                     local(%digits) = (%digits,'t',10,'e',11);
		     parse_nm();
		 }

             Note that local() is a run-time command, and so gets
             executed every time through a loop.  In Perl 4 it
             used  up more stack storage each time until the loop 
             was exited.  Perl 5 reclaims the space each time
             through, but it's still more efficient to declare
             your variables outside the loop.

             When you assign to a localized EXPR, the local
             doesn't change whether EXPR is viewed as a scalar or
             an array.  So

                 local($foo) = <STDIN>;
                 local @FOO = <STDIN>;

             both supply a list context to the righthand side,
             while

                 local $foo = <STDIN>;

             supplies a scalar context.

     localtime EXPR
             Converts a time as returned by the time function to
             a 9-element array with the time analyzed for the
             local timezone.  Typically used as follows:

                 ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) =
                                                             localtime(time);

             All array elements are numeric, and come straight
             out of a struct tm.  In particular this means that
             $mon has the range 0..11 and $wday has the range
             0..6.  If EXPR is omitted, does localtime(time).

             In a scalar context, prints out the ctime(3) value:

                 $now_string = localtime;  # e.g. "Thu Oct 13 04:54:34 1994"

             See also the timelocal entry in the perlmod manpage
             and the strftime(3) function available via the POSIX
             modulie.

     log EXPR
             Returns logarithm (base e) of EXPR.  If EXPR is
             omitted, returns log of $_.

     lstat FILEHANDLE
  
     lstat EXPR
             Does the same thing as the stat() function, but
             stats a symbolic link instead of the file the
             symbolic link points to.  If symbolic links are
             unimplemented on your system, a normal stat() is
             done.
  
     m//     The match operator.  See the perlop manpage.
  
     map BLOCK LIST
  

     map EXPR,LIST
             Evaluates the BLOCK or EXPR for each element of LIST
             (locally setting $_ to each element) and returns the
             list value composed of the results of each such
             evaluation.  Evaluates BLOCK or EXPR in a list
             context, so each element of LIST may produce zero,
             one, or more elements in the returned value.

                 @chars = map(chr, @nums);

             translates a list of numbers to the corresponding
             characters.  And

                 %hash = map {&key($_), $_} @array;

             is just a funny way to write

                 %hash = ();
                 foreach $_ (@array) {
                     $hash{&key($_)} = $_;
                 }


     mkdir FILENAME,MODE
             Creates the directory specified by FILENAME, with
             permissions specified by MODE (as modified by
             umask).  If it succeeds it returns 1, otherwise it
             returns 0 and sets $! (errno).

     msgctl ID,CMD,ARG
             Calls the System V IPC function msgctl.  If CMD is
             &IPC_STAT, then ARG must be a variable which will
             hold the returned msqid_ds structure.  Returns like
             ioctl: the undefined value for error, "0 but true"
             for zero, or the actual return value otherwise.

     msgget KEY,FLAGS
             Calls the System V IPC function msgget.  Returns the
             message queue id, or the undefined value if there is
             an error.
    
     msgsnd ID,MSG,FLAGS
             Calls the System V IPC function msgsnd to send the
             message MSG to the message queue ID.  MSG must begin
             with the long integer message type, which may be
             created with pack("L", $type).  Returns TRUE if
             successful, or FALSE if there is an error.
   
     msgrcv ID,VAR,SIZE,TYPE,FLAGS
             Calls the System V IPC function msgrcv to receive a
             message from message queue ID into variable VAR with
             a maximum message size of SIZE.  Note that if a
             message is received, the message type will be the
             first thing in VAR, and the maximum length of VAR is
             SIZE plus the size of the message type.  Returns
             TRUE if successful, or FALSE if there is an error.

     my EXPR A "my" declares the listed variables to be local
             (lexically) to the enclosing block, subroutine, eval
             or "do".  If more than one value is listed, the list
             must be placed in parens.  All the listed elements
             must be legal lvalues.  Only alphanumeric
             identifiers may be lexically scoped--magical
             builtins like $/ must be localized with "local"
             instead.  In particular, you're not allowed to say

                 my $_;      # Illegal.

             Unlike the "local" declaration, variables declared
             with "my" are totally hidden from the outside world,
             including any called subroutines (even if it's the
             same subroutine--every call gets its own copy).

             (An eval(), however, can see the lexical variables
             of the scope it is being evaluated in so long as the
             names aren't hidden by declarations within the
             eval() itself.  See the perlref manpage.)

             The EXPR may be assigned to if desired, which allows
             you to initialize your variables.  (If no
             initializer is given for a particular variable, it
             is created with an undefined value.)  Commonly this
             is used to name the parameters to a subroutine.
             Examples:

                 sub RANGEVAL {
                     my($min, $max, $thunk) = @_;
                     my $result = '';
                     my $i;

                     # Presumably $thunk makes reference to $i
  
                     for ($i = $min; $i <$max; $i++) { $result .="eval" $thunk; } $result; } if ($sw eq '-v') { # init my array with global array my @ARGV="@ARGV;" unshift(@ARGV,'echo'); system @ARGV; } # Outer @ARGV again visible When you assign to the EXPR, the "my" doesn't change whether EXPR is viewed as a scalar or an array. So my($foo)="<STDIN>;" my @FOO="<STDIN>;" both supply a list context to the righthand side, while my $foo="<STDIN>;" supplies a scalar context. Some users may wish to encourage the use of lexically scoped variables. As an aid to catching implicit references to package variables, if you say use strict 'vars'; then any variable reference from there to the end of the enclosing block must either refer to a lexical variable, or must be fully qualified with the package name. A compilation error results otherwise. An inner block may countermand this with "no strict 'vars'". next LABEL next The next command is like the continue statement in C; it starts the next iteration of the loop: line: while (<STDIN>) { next line if /^#/; # discard comments ... } Note that if there were a continue block on the above, it would get executed even on discarded lines. If the LABEL is omitted, the command refers to the innermost enclosing loop. no Module LIST See the "use" function, which "no" is the opposite of. oct EXPR Returns the decimal value of EXPR interpreted as an octal string. (If EXPR happens to start off with 0x, interprets it as a hex string instead.) The following will handle decimal, octal, and hex in the standard Perl or C notation: $val="oct($val)" if $val="~" /^0/; If EXPR is omitted, uses $_. open FILEHANDLE,EXPR open FILEHANDLE Opens the file whose filename is given by EXPR, and associates it with FILEHANDLE. If FILEHANDLE is an expression, its value is used as the name of the real filehandle wanted. If EXPR is omitted, the scalar variable of the same name as the FILEHANDLE contains the filename. If the filename begins with "<" or nothing, the file is opened for input. If the filename begins with ">", the file is opened for output. If the filename begins with ">>", the file is opened for appending. (You can put a '+' in front of the '>' or '<' to indicate that you want both read and write access to the file.) If the filename begins with "|", the filename is interpreted as a command to which output is to be piped, and if the filename ends with a "|", the filename is interpreted as command which pipes input to us. (You may not have a command that pipes both in and out.) Opening '-' opens STDIN and opening '>-' opens STDOUT. Open returns non-zero upon success, the undefined value otherwise. If the open involved a pipe, the return value happens to be the pid of the subprocess. Examples: $ARTICLE="100;" open ARTICLE or die "Can't find article $ARTICLE: $!0; while (<ARTICLE>) {... open(LOG, '>>/usr/spool/news/twitlog'); # (log is reserved) open(article, "caesar <$article |"); # decrypt article open(extract, "|sort>/tmp/Tmp$$");      # $$ is our process id
    
                 # process argument list of files along with any includes
  
                 foreach $file (@ARGV) {
                    process($file, 'fh00');
                 }
    
                 sub process {
                     local($filename, $input) = @_;
                     $input++;               # this is a string increment
                     unless (open($input, $filename)) {
                         print STDERR "Can't open $filename: $!\n";
                         return;
                     }

                     while (<$input>) {      # note use of indirection
                        if (/^#include "(.*)"/) {
                            process($1, $input);
                            next;
                        }
                        ...         # whatever
                     }
                 }
    

             You may also, in the Bourne shell tradition, specify
             an EXPR beginning with ">&", in which case the rest
             of the string is interpreted as the name of a
             filehandle (or file descriptor, if numeric) which is
             to be duped and opened.  You may use & after >, >>,
             <, +>, +>> and +<.  The mode you specify should
             match the mode of the original filehandle.  Here is
             a script that saves, redirects, and restores STDOUT
             and STDERR:

                 #!/usr/bin/perl
                 open(SAVEOUT, ">&STDOUT");
                 open(SAVEERR, ">&STDERR");
  
                 open(STDOUT, ">foo.out") || die "Can't redirect stdout";
                 open(STDERR, ">&STDOUT") || die "Can't dup stdout";
  
                 select(STDERR); $| = 1;     # make unbuffered
                 select(STDOUT); $| = 1;     # make unbuffered
   
                 print STDOUT "stdout 1\n";  # this works for
                 print STDERR "stderr 1\n";  # subprocesses too
    
	         close(STDOUT);
                 close(STDERR);

                 open(STDOUT, ">&SAVEOUT");
                 open(STDERR, ">&SAVEERR");

                 print STDOUT "stdout 2\n;
                 print STDERR "stderr 2\n;

             If you specify "<&=N", where N is a number, then
             Perl will do an equivalent of C's fdopen() of that
             file descriptor.  For example:

                 open(FILEHANDLE, "<&=$fd")

             If you open a pipe on the command "-", i.e. either
             "|-" or "-|", then there is an implicit fork done,
             and the return value of open is the pid of the child
             within the parent process, and 0 within the child
             process.  (Use defined($pid) to determine whether
             the open was successful.) The filehandle behaves
             normally for the parent, but i/o to that filehandle
             is piped from/to the STDOUT/STDIN of the child
             process.  In the child process the filehandle isn't
             opened--i/o happens from/to the new STDOUT or STDIN.
             Typically this is used like the normal piped open
             when you want to exercise more control over just how
             the pipe command gets executed, such as when you are
             running setuid, and don't want to have to scan shell
             commands for metacharacters.  The following pairs
             are more or less equivalent:

                 open(FOO, "|tr '[a-z]' '[A-Z]'");
                 open(FOO, "|-") || exec 'tr', '[a-z]', '[A-Z]';

                 open(FOO, "cat -n '$file'|");
                 open(FOO, "-|") || exec 'cat', '-n', $file;

             Explicitly closing any piped filehandle causes the
             parent process to wait for the child to finish, and
             returns the status value in $?.  Note: on any
             operation which may do a fork, unflushed buffers
             remain unflushed in both processes, which means you
             may need to set $| to avoid duplicate output.
  
             The filename that is passed to open will have
             leading and trailing whitespace deleted.  In order
             to open a file with arbitrary weird characters in
             it, it's necessary to protect any leading and
             trailing whitespace thusly:
  
                     $file =~ s#^(\s)#./$1#;
                     open(FOO, "<$file\0"); opendir DIRHANDLE,EXPR Opens a directory named EXPR for processing by readdir(), telldir(), seekdir(), rewinddir() and
             closedir().  Returns TRUE if successful.  DIRHANDLEs
             have their own namespace separate from  FILEHANDLEs.

     ord EXPR
             Returns the numeric ascii value of the first
             character of EXPR.  If EXPR is omitted, uses $_.

     pack TEMPLATE,LIST
             Takes an array or list of values and packs it into a
             binary structure, returning the string containing
             the structure.  The TEMPLATE is a sequence of
             characters that give the order and type of values,
             as follows:

                 A   An ascii string, will be space padded.
                 a   An ascii string, will be null padded.
                 b   A bit  string  (ascending bit order, like vec()).
                 B   A bit string (descending bit order).
                 h   A hex string (low nybble first).
                 H   A hex string (high nybble first).

                 c   A signed char value.
                 C   An unsigned char value.
                 s   A signed short value.
                 S   An unsigned short value.
                 i   A signed integer value.
                 I   An unsigned integer value.
                 l   A signed long value.
                 L   An unsigned long value.

                 n   A short in "network" order.
                 N   A long in "network" order.
                 v   A short in "VAX" (little-endian) order.
                 V   A long in "VAX" (little-endian) order.
 
                 f   A single-precision float in the native format.
                 d   A double-precision float in the native format.
  
                 p   A pointer to a null-terminated string.
                 P   A pointer to a structure (fixed-length string).
  
                 u   A uuencoded string.
  
                 x   A null byte.
                 X   Back up a byte.
                 @   Null fill to absolute position.

             Each letter may optionally be followed by a number
             which gives a repeat count.  With all types except
             "a", "A", "b", "B", "h" and "H", and "P" the pack
             function will gobble up that many values from the
             LIST.  A * for the repeat count means to use however
             many items are left.  The "a" and "A" types gobble
             just one value, but pack it as a string of length
             count, padding with nulls or spaces as necessary.
             (When unpacking, "A" strips trailing spaces and
             nulls, but "a" does not.)  Likewise, the "b" and "B"
             fields pack a string that many bits long.  The "h"
             and "H" fields pack a string that many nybbles long.
             The "P" packs a pointer to a structure of the size
             indicated by the length.  Real numbers (floats and
             doubles) are in the native machine format only; due
             to the multiplicity of floating formats around, and
             the lack of a standard "network" representation, no
             facility for interchange has been made.  This means
             that packed floating point data written on one
             machine may not be readable on another - even if
             both use IEEE floating point arithmetic (as the
             endian-ness of the memory representation is not part
             of the IEEE spec).  Note that Perl uses doubles
             internally for all numeric calculation, and
             converting from double into float and thence back to
             double again will lose precision (i.e.  unpack("f",
             pack("f", $foo)) will not in general equal $foo).

             Examples:

                 $foo = pack("cccc",65,66,67,68);
                 # foo eq "ABCD"
                 $foo = pack("c4",65,66,67,68);
                 # same thing

                 $foo = pack("ccxxcc",65,66,67,68);
                 # foo eq "AB\0\0CD"
 
                 $foo = pack("s2",1,2);
                 # "\1\0\2\0" on little-endian
                 # "\0\1\0\2" on big-endian
  
                 $foo = pack("a4","abcd","x","y","z");
                 # "abcd"
  
                 $foo = pack("aaaa","abcd","x","y","z");
                 # "axyz"

                 $foo = pack("a14","abcdefg");
                 # "abcdefg\0\0\0\0\0\0\0"

                 $foo = pack("i9pl", gmtime);
                 # a real struct tm (on my system anyway)

                 sub bintodec {
                     unpack("N", pack("B32", substr("0" x 32 . shift, -32)));
                 }

             The same template may generally also be used in the
             unpack function.

     pipe READHANDLE,WRITEHANDLE
             Opens a pair of connected pipes like the
             corresponding system call.  Note that if you set up
             a loop of piped processes, deadlock can occur unless
             you are very careful.  In addition, note that Perl's
             pipes use stdio buffering, so you may need to set $|
             to flush your WRITEHANDLE after each command,
             depending on the application.

     pop ARRAY
             Pops and returns the last value of the array,
             shortening the array by 1.  Has a similar effect to

                 $tmp = $ARRAY[$#ARRAY--];

             If there are no elements in the array, returns the
             undefined value.

     pos SCALAR
             Returns the offset of where the last m//g search
             left off for the variable in question.  May be
             modified to change that offset.

     print FILEHANDLE LIST

     print LIST

     print   Prints a string or a comma-separated list of
             strings.  Returns non-zero if successful.
             FILEHANDLE may be a scalar variable name, in which
             case the variable contains the name of the
             filehandle, thus introducing one level of
             indirection.  (NOTE: If FILEHANDLE is a variable and
             the next token is a term, it may be misinterpreted
             as an operator unless you interpose a + or put
             parens around the arguments.)  If FILEHANDLE is
             omitted, prints by default to standard output (or to
             the last selected output channel--see select()). If
             LIST is also omitted, prints $_ to STDOUT.  To set
             the default output channel to something other than
             STDOUT use the select operation.  Note that, because
             print takes a LIST, anything in the LIST is
             evaluated in a list context, and any subroutine that
             you call will have one or more of its expressions
             evaluated in a list context.  Also be careful not to
             follow the print keyword with a left parenthesis
             unless you want the corresponding right parenthesis
             to terminate the arguments to the print--interpose a
             + or put parens around all the arguments.

     printf FILEHANDLE LIST

     printf LIST
             Equivalent to a "print FILEHANDLE sprintf(LIST)".
             The first argument of the list will be interpreted
             as the printf format.

     push ARRAY,LIST
             Treats ARRAY as a stack, and pushes the values of
             LIST onto the end of ARRAY.  The length of ARRAY
             increases by the length of LIST.  Has the same
             effect as

                 for $value (LIST) {
                     $ARRAY[++$#ARRAY] = $value;
                 }

             but is more efficient.  Returns the new number of
             elements in the array.

     q/STRING/

     qq/STRING/

     qx/STRING/

     qw/STRING/
             Generalized quotes.  See the perlop manpage.
  
     quotemeta EXPR
              Returns the value of EXPR with with all regular
              expression metacharacters backslashed.  This is the
              internal function implementing the \Q escape in
              double-quoted strings.
  
     rand EXPR
   
     rand    Returns a random fractional number between 0 and the
             value of EXPR.  (EXPR should be positive.)  If EXPR
             is omitted, returns a value between 0 and 1.  This
             function produces repeatable sequences unless
             srand() is invoked.  See also srand().

             (Note: if your rand function consistently returns
             numbers that are too large or too small, then your
             version of Perl was probably compiled with the wrong
             number of RANDBITS.  As a workaround, you can
             usually multiply EXPR by the correct power of 2 to
             get the range you want.  This will make your script
             unportable, however.  It's better to recompile if
             you can.)

     read FILEHANDLE,SCALAR,LENGTH,OFFSET

     read FILEHANDLE,SCALAR,LENGTH
             Attempts to read LENGTH bytes of data into variable
             SCALAR from the specified FILEHANDLE.  Returns the
             number of bytes actually read, or undef if there was
             an error.  SCALAR will be grown or shrunk to the
             length actually read.  An OFFSET may be specified to
             place the read data at some other place than the
             beginning of the string.  This call is actually
             implemented in terms of stdio's fread call.  To get
             a true read system call, see sysread().

     readdir DIRHANDLE
             Returns the next directory entry for a directory
             opened by opendir().  If used in a list context,
             returns all the rest of the entries in the
             directory.  If there are no more entries, returns an
             undefined value in a scalar context or a null list
             in a list context.

     readlink EXPR
             Returns the value of a symbolic link, if symbolic
             links are implemented.  If not, gives a fatal error.
             If there is some system error, returns the undefined
             value and sets $! (errno).  If EXPR is omitted, uses
             $_.
  
     recv SOCKET,SCALAR,LEN,FLAGS
             Receives a message on a socket.  Attempts to receive
             LENGTH bytes of data into variable SCALAR from the
             specified SOCKET filehandle.  Actually does a C
             recvfrom(), so that it can returns the address of
             the sender.  Returns the undefined value if there's
             an error.  SCALAR will be grown or shrunk to the
             length actually read.  Takes the same flags as the
             system call of the same name.
   
     redo LABEL
 
     redo    The redo command restarts the loop block without
             evaluating the conditional again.  The continue
             block, if any, is not executed.  If the LABEL is
             omitted, the command refers to the innermost
             enclosing loop.  This command is normally used by
             programs that want to lie to themselves about what
             was just input:

                 # a simpleminded Pascal comment stripper
                 # (warning: assumes no { or } in strings)
                 line: while (<STDIN>) {
                     while (s|({.*}.*){.*}|$1 |) {}
                     s|{.*}| |;
                     if (s|{.*| |) {
                         $front = $_;
                         while (<STDIN>) {
                             if (/}/) {      # end of comment?
                                 s|^|$front{|;
                                 redo line;
                             }
                         }
                     }
                     print;
                 }
 
  
     ref EXPR
             Returns a TRUE value if EXPR is a reference, FALSE
             otherwise.  The value returned depends on the type
             of thing the reference is a reference to.  Builtin
             types include:
  
                 REF
                 SCALAR
                 ARRAY
                 HASH
                 CODE
                 GLOB

             If the referenced object has been blessed into a
             package, then that package name is returned instead.
             You can think of ref() as a typeof() operator.

                 if (ref($r) eq "HASH") {
                     print "r is a reference to an associative array.0;
                 }
                 if (!ref ($r) {
                     print "r is not a reference at all.0;
                 }

             See also the perlref manpage.

     rename OLDNAME,NEWNAME
             Changes the name of a file.  Returns 1 for success,
             0 otherwise.  Will not work across filesystem
             boundaries. 

     require EXPR

     require Demands some semantics specified by EXPR, or by $_
             if EXPR is not supplied.  If EXPR is numeric,
             demands that the current version of Perl ($] or
             $PERL_VERSION) be equal or greater than EXPR.

             Otherwise, demands that a library file be included
             if it hasn't already been included.  The file is
             included via the do-FILE mechanism, which is
             essentially just a variety of eval().  Has semantics
             similar to the following subroutine:

                 sub require {
                     local($filename) = @_;
                     return 1 if $INC{$filename};
                     local($realfilename,$result);
                     ITER: {
                         foreach $prefix (@INC) {
                            $realfilename = "$prefix/$filename";
                            if (-f $realfilename) {
                                $result = do $realfilename;
                                last ITER;
                            }
                         }
                         die "Can't find $filename in \@INC";
                     }
                     die $@ if $@;
                     die "$filename did not return true value" unless $result;

                     $INC{$filename} = $realfilename;
                     $result;
                 }

             Note that the file will not be included twice under
             the same specified name.  The file must return TRUE
             as the last statement to indicate successful
             execution of any initialization code, so it's
             customary to end such a file with "1;" unless you're
             sure it'll return TRUE otherwise.  But it's better
             just to put the "1;", in case you add more
             statements.

             If EXPR is a bare word, the require assumes a ".pm"
             extension for you, to make it easy to load standard
             modules.  This form of loading of modules does not
             risk altering your namespace.

             For a yet more powerful import facility, see the the
             use() entry elsewhere in this documentbelow, and
             also the perlmod manpage.

     reset EXPR

     reset   Generally used in a continue block at the end of a
             loop to clear variables and reset ?? searches so
             that they work again.  The expression is interpreted
             as a list of single characters (hyphens allowed for
             ranges).  All variables and arrays beginning with
             one of those letters are reset to their pristine
             state.  If the expression is omitted, one-match
             searches (?pattern?) are reset to match again.  Only
             resets variables or searches in the current package.
             Always returns 1.  Examples:

                 reset 'X';          # reset all X variables
                 reset 'a-z';        # reset lower case variables
                 reset;              # just reset ?? searches

 
             Resetting "A-Z" is not recommended since you'll wipe
             out your ARGV and ENV arrays.  Only resets package
             variables--lexical variables are unaffected, but
             they clean themselves up on scope exit anyway, so
             anymore you probably want to use them instead.  See
             the my entry elsewhere in this document.
   
     return LIST
             Returns from a subroutine or eval with the value
             specified.  (Note that in the absence of a return a
             subroutine or eval will automatically return the
             value of the last expression evaluated.)

     reverse LIST
             In a list context, returns a list value consisting
             of the elements of LIST in the opposite order.  In a
             scalar context, returns a string value consisting of
             the bytes of the first element of LIST in the
             opposite order.

     rewinddir DIRHANDLE
             Sets the current position to the beginning of the
             directory for the readdir() routine on DIRHANDLE.

     rindex STR,SUBSTR,POSITION

     rindex STR,SUBSTR
             Works just like index except that it returns the
             position of the LAST occurrence of SUBSTR in STR.
             If POSITION is specified, returns the last
             occurrence at or before that position.

     rmdir FILENAME
             Deletes the directory specified by FILENAME if it is
             empty.  If it succeeds it returns 1, otherwise it
             returns 0 and sets $! (errno).  If FILENAME is
             omitted, uses $_.

     s///    The substitution operator.  See the perlop  manpage.

     scalar EXPR
             Forces EXPR to be interpreted in a scalar context
             and returns the value of EXPR.

     seek FILEHANDLE,POSITION,WHENCE
             Randomly positions the file pointer for FILEHANDLE,
             just like the fseek() call of stdio.  FILEHANDLE may
             be an expression whose value gives the name of the
             filehandle.  The values for WHENCE are 0 to set the
             file pointer to POSITION, 1 to set the it to current
             plus POSITION, and 2 to set it to EOF plus offset.
             You may use the values SEEK_SET, SEEK_CUR, and
             SEEK_END for this is usin the POSIX module.  Returns
             1 upon success, 0 otherwise.
  
     seekdir DIRHANDLE,POS
             Sets the current position for the readdir() routine
             on DIRHANDLE.  POS must be a value returned by
             telldir().  Has the same caveats about possible
             directory compaction as the corresponding system
             library routine.
   
     select FILEHANDLE  

     select  Returns the currently selected filehandle.  Sets the
             current default filehandle for output, if FILEHANDLE
             is supplied.  This has two effects: first, a write
             or a print without a filehandle will default to this
             FILEHANDLE.  Second, references to variables related
             to output will refer to this output channel.  For
             example, if you have to set the top of form format
             for more than one output channel, you might do the
             following:

                 select(REPORT1);
                 $^ = 'report1_top';
                 select(REPORT2);
                 $^ = 'report2_top';

             FILEHANDLE may be an expression whose value gives
             the name of the actual filehandle.  Thus:

                 $oldfh = select(STDERR); $| = 1; select($oldfh);

             With Perl 5, filehandles are objects with methods,
             and the last example is preferably written

                 use FileHandle;
                 STDERR->autoflush(1);

     select RBITS,WBITS,EBITS,TIMEOUT
             This calls the select system(2) call with the
             bitmasks specified, which can be constructed using
             fileno() and vec(), along these lines:

                 $rin = $win = $ein = '';
                 vec($rin,fileno(STDIN),1) = 1;
                 vec($win,fileno(STDOUT),1) = 1;
                 $ein = $rin | $win;

             If you want to select on many filehandles you might
             wish to write a subroutine:

                 sub fhbits {
		     local(@fhlist) = split(' ',$_[0]);
		     local($bits);
		     for (@fhlist) {
			vec($bits,fileno($_),1) = 1;
		     }
		     $bits;
		 }
		 $rin = &fhbits('STDIN TTY SOCK');

	     The usual idiom is:

	         ($nfound,$timeleft) =
                   select($rout=$rin, $wout=$win,$eout=$ein, $timeout);

             or to block until something becomes ready:

                 $nfound = select($rout=$rin, $wout=$win, $eout=$ein, undef);

             Any of the bitmasks can also be undef.  The timeout,
             if specified, is in seconds, which may be
             fractional.  Note: not all implementations are
             capable of returning the $timeleft.  If not, they
             always return $timeleft equal to the supplied
             $timeout.

             You can effect a 250 microsecond sleep this way:

                 select(undef, undef, undef, 0.25);


     semctl ID,SEMNUM,CMD,ARG
             Calls the System V IPC function semctl.  If CMD is
             &IPC_STAT or &GETALL, then ARG must be a variable
             which will hold the returned semid_ds structure or
             semaphore value array.  Returns like ioctl: the
             undefined value for error, "0 but true" for zero, or
             the actual return value otherwise.

     semget KEY,NSEMS,FLAGS
             Calls the System V IPC function semget.  Returns the
             semaphore id, or the undefined value if there is an
             error.

     semop KEY,OPSTRING
             Calls the System V IPC function semop to perform
             semaphore operations such as signaling and  waiting.
             OPSTRING must be a packed array of semop structures.
             Each semop structure can be generated with
             pack("sss", $semnum, $semop, $semflag).  The number
             of semaphore operations is implied by the length of
	     OPSTRING.  Returns TRUE if successful, or FALSE if
	     there is an error.  As an example, the following
             code waits on semaphore $semnum of semaphore id
             $semid:
  
                  $semop = pack("sss", $semnum, -1, 0);
                  die "Semaphore trouble: $!\n" unless semop($semid, $semop);
  
             To signal the semaphore, replace "-1" with "1".
  
     send SOCKET,MSG,FLAGS,TO
 	       

     send SOCKET,MSG,FLAGS
             Sends a message on a socket.  Takes the same flags
             as the system call of the same name.  On unconnected
             sockets you must specify a destination to send TO,
             in which case it does a C sendto().  Returns the
             number of characters sent, or the undefined value if
             there is an error.

     setpgrp PID,PGRP
             Sets the current process group for the specified
             PID, 0 for the current process.  Will produce a
             fatal error if used on a machine that doesn't
             implement setpgrp(2).

     setpriority WHICH,WHO,PRIORITY
             Sets the current priority for a process, a process
             group, or a user.  (See Lsetpriority(2)>.)  Will
             produce a fatal error if used on a machine that
             doesn't implement setpriority(2).

     setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL
             Sets the socket option requested.  Returns undefined
             if there is an error.  OPTVAL may be specified as
             undef if you don't want to pass an argument.

     shift ARRAY

     shift   Shifts the first value of the array off and returns
             it, shortening the array by 1 and moving everything
             down.  If there are no elements in the array,
             returns the undefined value.  If ARRAY is omitted,
             shifts the @ARGV array in the main program, and the
             @_ array in subroutines.  (This is determined
             lexically.)  See also unshift(), push(), and  pop().
             Shift() and unshift() do the same thing to the left
             end of an array that push() and pop() do to the
             right end.

      shmctl ID,CMD,ARG
             Calls the System V IPC function shmctl.  If CMD is
             &IPC_STAT, then ARG must be a variable which will
             hold the returned shmid_ds structure.  Returns like
             ioctl: the undefined value for error, "0 but true"
             for zero, or the actual return value otherwise.
    
      shmget KEY,SIZE,FLAGS
             Calls the System V IPC function shmget.  Returns the
             shared memory segment id, or the undefined value if
             there is an error.
  

     shmread ID,VAR,POS,SIZE

     shmwrite ID,STRING,POS,SIZE
             Reads or writes the System V shared memory segment
             ID starting at position POS for size SIZE by
             attaching to it, copying in/out, and detaching from
             it.  When reading, VAR must be a variable which will
             hold the data read.  When writing, if STRING is too
             long, only SIZE bytes are used; if STRING is too
             short, nulls are written to fill out SIZE bytes.
             Return TRUE if successful, or FALSE if there is an
             error.

     shutdown SOCKET,HOW
             Shuts down a socket connection in the manner
             indicated by HOW, which has the same interpretation
             as in the system call of the same name.

     sin EXPR
             Returns the sine of EXPR (expressed in radians).  If
             EXPR is omitted, returns sine of $_.

     sleep EXPR

     sleep   Causes the script to sleep for EXPR seconds, or
             forever if no EXPR.  May be interrupted by sending
             the process a SIGALRM.  Returns the number of
             seconds actually slept.  You probably cannot mix
             alarm() and sleep() calls, since sleep() is often
             implemented using alarm().

             On some older systems,it may sleep up to a full
             second less than what you requested, depending on
             how it counts seconds.  Most modern systems always
             sleep the full amount.

     socket SOCKET,DOMAIN,TYPE,PROTOCOL
             Opens a socket of the specified kind and attaches it
             to filehandle SOCKET.  DOMAIN, TYPE and PROTOCOL are
             specified the same as for the system call of the
             same name.  You should "use Socket;" first to get
             the proper definitions imported.  See the example in
             the perlipc manpage.
  
     socketpair SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL
             Creates an unnamed pair of sockets in the specified
             domain, of the specified type.  DOMAIN, TYPE and
             PROTOCOL are specified the same as for the system
             call of the same name.  If unimplemented, yields a
             fatal error.  Returns TRUE if successful.
   
     sort SUBNAME LIST

     sort BLOCK LIST

     sort LIST
             Sorts the LIST and returns the sorted list value.
             Nonexistent values of arrays are stripped out.  If
             SUBNAME or BLOCK is omitted, sorts in standard
             string comparison order.  If SUBNAME is specified,
             it gives the name of a subroutine that returns an
             integer less than, equal to, or greater than 0,
             depending on how the elements of the array are to be
             ordered.  (The <=> and cmp operators are extremely
             useful in such routines.)  SUBNAME may be a scalar
             variable name, in which case the value provides the
             name of the subroutine to use.  In place of a
             SUBNAME, you can provide a BLOCK as an anonymous,
             in-line sort subroutine.

             In the interests of efficiency the normal calling
             code for subroutines is bypassed, with the following
             effects: the subroutine may not be a recursive
             subroutine, and the two elements to be compared are
             passed into the subroutine not via @_ but as $a and
             $b (see example below).  They are passed by
             reference, so don't modify $a and $b.

             Examples:


                 # sort lexically
                 @articles = sort @files;

                 # same thing, but with explicit sort routine
                 @articles = sort {$a cmp $b} @files;

                 # same thing in reversed order
                 @articles = sort {$b cmp $a} @files;

                 # sort numerically ascending
                 @articles = sort {$a <=> $b} @files;
                 # sort using explicit subroutine name
                 sub byage {
                     $age{$a} <=> $age{$b};  # presuming integers
                 }
                 @sortedclass = sort byage @class;
   
                 sub backwards { $b cmp $a; }
                 @harry = ('dog','cat','x','Cain','Abel');
                 @george = ('gone','chased','yz','Punished','Axed');
                 print sort @harry;
                         # prints AbelCaincatdogx
                 print sort backwards @harry;
                         # prints xdogcatCainAbel
                 print sort @george, 'to', @harry;
                         #  prints AbelAxedCainPunishedcatchaseddoggonetoxyz


     splice ARRAY,OFFSET,LENGTH,LIST

     splice ARRAY,OFFSET,LENGTH

     splice ARRAY,OFFSET
             Removes the elements designated by OFFSET and LENGTH
             from an array, and replaces them with the elements
             of LIST, if any.  Returns the elements removed from
             the array.  The array grows or shrinks as necessary.
             If LENGTH is omitted, removes everything from OFFSET
             onward.  The following equivalencies hold (assuming
             $[ == 0):

                 push(@a,$x,$y)      splice(@a,$#a+1,0,$x,$y)
                 pop(@a)             splice(@a,-1)
                 shift(@a)           splice(@a,0,1)
                 unshift(@a,$x,$y)   splice(@a,0,0,$x,$y)
                 $a[$x] = $y         splice(@a,$x,1,$y);

             Example, assuming array lengths are passed before
             arrays:

                 sub aeq {   # compare two list values
                     local(@a) = splice(@_,0,shift);
                     local(@b) = splice(@_,0,shift);
                     return  0 unless @a == @b;       # same len?
                     while (@a) {
                         return 0 if pop(@a) ne pop(@b);
                     }
		     return 1;
                 if (&aeq($len,@foo[1..$len],0+@bar,@bar)) { ... }
  
     split /PATTERN/,EXPR,LIMIT
  
     split /PATTERN/,EXPR
  
     split /PATTERN/
 
 
     split   Splits a string into an array of strings, and
             returns it.

             If not in a list context, returns the number of
             fields found and splits into the @_ array.  (In a
             list context, you can force the split into @_ by
             using ?? as the pattern delimiters, but it still
             returns the array value.)  The use of implicit split
             to @_ is deprecated, however.

             If EXPR is omitted, splits the $_ string.  If
             PATTERN is also omitted, splits on whitespace (/[
             0+/).  Anything matching PATTERN is taken to be
             a delimiter separating the fields.  (Note that the
             delimiter may be longer than one character.)  If
             LIMIT is specified and is not negative, splits into
             no more than that many fields (though it may split
             into fewer).  If LIMIT is unspecified, trailing null
             fields are stripped (which potential users of pop()
             would do well to remember).  If LIMIT is negative,
             it is treated as if an arbitrarily large LIMIT had
             been specified.

             A pattern matching the null string (not to be
             confused with a null pattern C<//., which is just
             one member of the set of patterns matching a null
             string) will split the value of EXPR into separate
             characters at each point it matches that way.  For
             example:

                 print join(':', split(/ */, 'hi there'));

             produces the output 'h:i:t:h:e:r:e'.

             The LIMIT parameter can be used to partially split a
             line

                 ($login, $passwd, $remainder) =  split(/:/,  $_,3);

             When assigning to a list, if LIMIT is omitted, Perl
             supplies a LIMIT one larger than the number of
             variables in the list, to avoid unnecessary work.
             For the list above LIMIT would have been 4 by
             default.  In time critical applications it behooves
             you not to split into more fields than you really
             need.
   
             If the PATTERN contains parentheses, additional
             array elements are created from each matching
             substring in the delimiter.
  
                 split(/([,-])/, "1-10,20");

             produces the list value

                 (1, '-', 10, ',', 20)

             The pattern /PATTERN/ may be replaced with an
             expression to specify patterns that vary at runtime.
             (To do runtime compilation only once, use
             /$variable/o.)  As a special case, specifying a
             space (' ') will split on white space just as split
             with no arguments does, but leading white space does
             NOT produce a null first field.  Thus, split(' ')
             can be used to emulate awk's default behavior,
             whereas split(/ /) will give you as many null
             initial fields as there are leading spaces.

             Example:

                 open(passwd, '/etc/passwd');
                 while (<passwd>) {
                     ($login,  $passwd, $uid, $gid, $gcos, $home,
$shell) = split(/:/);
                     ...
                 }

             (Note that $shell above will still have a newline on
             it.  See the chop, chomp,  and join entries
             elsewhere in this document.)

     sprintf FORMAT,LIST
             Returns a string formatted by the usual printf
             conventions of the C language.  (The * character for
             an indirectly specified length is not supported, but
             you can get the same effect by interpolating a
             variable into the pattern.)

     sqrt EXPR
             Return the square root of EXPR.  If EXPR is omitted,
             returns square root of $_.

     srand EXPR
             Sets the random number seed for the rand operator.
             If EXPR is omitted, does srand(time).  Of course,
             you'd need something much more random than that for
             cryptographic purposes, since it's easy to guess the
             current time.  Checksumming the compressed output of
             rapidly changing operating system status programs is
             the usual method.  Examples are posted regularly to
             comp.security.unix.
  
     stat FILEHANDLE
   
     stat EXPR
             Returns a 13-element array giving the status info
             for a file, either the file opened via FILEHANDLE,
             or named by EXPR.  Returns a null list if the stat
             fails.  Typically used as follows:

                 ($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,
                    $atime,$mtime,$ctime,$blksize,$blocks)
                        = stat($filename);

             If stat is passed the special filehandle consisting
             of an underline, no stat is done, but the current
             contents of the stat structure from the last stat or
             filetest are returned.  Example:

                 if (-x $file && (($d) = stat(_)) && $d < 0) {
                     print "$file is executable NFS file0;
                 }

             (This only works on machines for which the device
             number is negative under NFS.)

     study SCALAR

     study   Takes extra time to study SCALAR ($_ if unspecified)
             in anticipation of doing many pattern matches on the
             string before it is next modified.  This may or may
             not save time, depending on the nature and number of
             patterns you are searching on, and on the
             distribution of character frequencies in the string
             to be searched--you probably want to compare
             runtimes with and without it to see which runs
             faster.  Those loops which scan for many short
             constant strings (including the constant parts of
             more complex patterns) will benefit most.  You may
             have only one study active at a time--if you study a
             different scalar the first is "unstudied".  (The way
             study works is this: a linked list of every
             character in the string to be searched is made, so
             we know, for example, where all the 'k' characters
             are.  From each search string, the rarest character
             is selected, based on some static frequency tables
             constructed from some C programs and English text.
             Only those places that contain this "rarest"
             character are examined.)
  
             For example, here is a loop which inserts index
             producing entries before any line containing a
             certain pattern:
 
                 while (<>) {
                     study;              
                     print ".IX foo\n" if /\bfoo\b;
                     print ".IX bar\n" if /\bbbar\b/;
                     print ".IX blurfl\n" if /\bblurfl\b/;
                     ...                    
                     print;                 
                 }
                               
             In searching for /\bfoo\b/, only those locatations in
             $_ that contain "f" will be looked at, because "f"
             is rarer than "o".  In general, this is a big win
             except in pathological cases.  The only question is
             whether it saves you more time than it took to build
             the linked list in the first place.

             Note that if you have to look for strings that you
             don't know till runtime, you can build an entire
             loop as a string and eval that to avoid recompiling
             all your patterns all the time.  Together with
             undefining $/ to input entire files as one record,
             this can be very fast, often faster than specialized
             programs like fgrep(1).  The following scans a list
             of files (@files) for a list of words (@words), and
             prints out the names of those files that contain a
             match:

                 $search = 'while (<>) { study;';
                 foreach $word (@words) {
                     $search .= "++\$seen{\$ARGV} if /\\b$word\\b/;\n";
                 }
                 $search .= "}";
                 @ARGV = @files;
		 undef $/;
		 eval $search;		#this screams
		 $/ = "\n\;		#put back to normal input delim
		 foreach $file (sort keys(%seen)){
		    print $file, "\n";
		 }

    substr EXPR,OFFSET,LEN

    substr EXPR, OFFSET

             Extracts a substring out of EXPR and returns it.
             First character is at offset 0, or whatever you've
             set $[ to.  If OFFSET is negative, starts that far
             from the end of the string.  If LEN is omitted,
             returns everything to the end of the string.  You
             can use the substr() function as an lvalue, in which
             case EXPR must be an lvalue.  If you assign
             something shorter than LEN, the string will shrink,
             and if you assign something longer than LEN, the
             string will grow to accommodate it.  To keep the
             string the same length you may need to pad or chop
             your value using sprintf().

     symlink OLDFILE,NEWFILE
             Creates a new filename symbolically linked to the
             old filename.  Returns 1 for success, 0 otherwise.
             On systems that don't support symbolic links,
             produces a fatal error at run time.  To check for
             that, use eval:

                 $symlink_exists = (eval 'symlink("","");', $@ eq'');


     syscall LIST
             Calls the system call specified as the first element
             of the list, passing the remaining elements as
             arguments to the system call.  If unimplemented,
             produces a fatal error.  The arguments are
             interpreted as follows: if a given argument is
             numeric, the argument is passed as an int.  If not,
             the pointer to the string value is passed.  You are
             responsible to make sure a string is pre-extended
             long enough to receive any result that might be
             written into a string.  If your integer arguments
             are not literals and have never been interpreted in
             a numeric context, you may need to add 0 to them to
             force them to look like numbers.

                 require  'syscall.ph';         # may need 2ph

	     Note that Perl only supports passing of up to 14
	     arguments to your system call, which in practice 
	     should usually suffice.
    s
     sysread FILEHANDLE,SCALAR,LENGTH,OFFSET
   
     sysread FILEHANDLE,SCALAR,LENGTH
	     Attempts to read LENGHT bytes of date into variable
             SCALAR from the specified FILEHANDLE, using the
             system call read(2).  It bypasses stdio, so mixing
             this  with other kinds of reads may cause confusion.
             Returns the number of bytes actually read, or undef
             if there was an error.  SCALAR will be grown or
             shrunk to the length actually read.  An OFFSET may
             be specified to place the read data at some other
             place than the beginning of the string.

     system LIST
             Does exactly the same thing as "exec LIST" except
             that a fork is done first, and the parent process
             waits for the child process to complete.  Note that
             argument processing varies depending on the number
             of arguments.  The return value is the exit status
             of the program as returned by the wait() call.  To
             get the actual exit value divide by 256.  See also
             the exec entry elsewhere in this document.

     syswrite FILEHANDLE,SCALAR,LENGTH,OFFSET

     syswrite FILEHANDLE,SCALAR,LENGTH
             Attempts to write LENGTH bytes of data from variable
             SCALAR to the specified FILEHANDLE, using the system
             call write(2).  It bypasses stdio, so mixing this
             with prints may cause confusion.  Returns the number
             of bytes actually written, or undef if there was an
             error.  An OFFSET may be specified to place the read
             data at some other place than the beginning of the
             string.

     tell FILEHANDLE

     tell    Returns the current file position for FILEHANDLE.
             FILEHANDLE may be an expression whose value gives
             the name of the actual filehandle.  If FILEHANDLE is
             omitted, assumes the file last read.

     telldir DIRHANDLE
	     Returns the current position of the readdir()
             routines on DIRHANDLE.  Value may be given to
	     seekdir() to access a particular location in a
	     directory.  Has the same caveats about possible
	     directory compaction as the corresponding system
	     library routine.

     tie VARIABLE,PACKAGENAME,LIST
	     This function binds a varialbe to a package that
	     will provide the implementation for the variable.
	     VARIABLE is the name of the variable to be
	     enchanted.  PACKAGENAME is the name of a package
	     implementing objects of correct type.  Any
             additional arguments are passed to the "new" method
             of the package.  Typically these are arguments such
             as  might be passed to the dbm_open() function of C.

             Note that functions such as keys() and values() may
             return huge array values when used on large DBM
             files.  You may prefer to use the each() function to
             iterate over large DBM files.  Example:

                 # print out history file offsets
                 tie(%HIST,  NDBM_File,  '/usr/lib/news/history', 1, 0);
                 while (($key,$val) = each %HIST) {
                     print $key, ' = ', unpack('L',$val), "0;
                 }
                 untie(%HIST);

             A package implementing an associative array should
             have the following methods:

                 TIEHASH objectname, LIST
                 DESTROY this
                 FETCH this, key
                 STORE this, key, value
                 DELETE this, key
                 EXISTS this, key
                 FIRSTKEY this
                 NEXTKEY this, lastkey

             A package implementing an ordinary array should have
             the following methods:

                 TIEARRAY objectname, LIST
                 DESTROY this
                 FETCH this, key
                 STORE this, key, value
                 [others TBD]

             A package implementing a scalar should have the
             following methods:

		 TIESCALAR objectname, LIST
		 DESTROY this
		 FETCH this
		 STORE this, value

     time    Returns the number of non-leap seconds since
	     00:00:00 UTC, January 1, 1970.  Suitable for feeding
	     to gmtime() and localtime().

     times   Returns a four-element array giving the user and 
             system times, in seconds, for this process and the
             children of this process.

                 ($user,$system,$cuser,$csystem) = times;


     tr///   The translation operator.  See the perlop manpage.

     truncate FILEHANDLE,LENGTH

     truncate EXPR,LENGTH
             Truncates the file opened on FILEHANDLE, or named by
             EXPR, to the specified length.  Produces a fatal
             error  if truncate isn't implemented on your system.

     uc EXPR Returns an uppercased version of EXPR.  This is the
             internal function implementing the U escape in
             double-quoted strings.

     ucfirst EXPR
             Returns the value of EXPR with the first character
             uppercased.  This is the internal function
             implementing the \u  escape in double-quoted strings.

     umask EXPR

     umask   Sets the umask for the process and returns the old
             one.  If EXPR is omitted, merely returns current
             umask.

     undef EXPR

     undef   Undefines the value of EXPR, which must be an
             lvalue.  Use only on a scalar value, an entire
             array, or a subroutine name (using "&").  (Using
             undef() will probably not do what you expect on most
             predefined variables or DBM list values, so don't do
             that.)  Always returns the undefined value.  You can
             omit the EXPR, in which case nothing is undefined,
             but you still get an undefined value that you could,
	     for instance, return from a subroutin.  Examples:
		 
		 undef $foo;
		 undef $bar{'blurfl'};
		 undef @ary;
		 undef %assoc;
		 undef &mysub;
		 return (wantarry ? (): undef) if $they_blew_it;

    unlink LIST
             Deletes a list of files.  Returns the number of
             files successfully deleted.

                 $cnt = unlink 'a', 'b', 'c';
                 unlink @goners;
                 unlink <*.bak>;

             Note: unlink will not delete directories unless you
             are superuser and the -U flag is supplied to Perl.
             Even if these conditions are met, be warned that
             unlinking a directory can inflict damage on your
             filesystem.  Use rmdir instead.

     unpack TEMPLATE,EXPR
             Unpack does the reverse of pack: it takes a string
             representing a structure and expands it out into a
             list value, returning the array value.  (In a scalar
             context, it merely returns the first value
             produced.)  The TEMPLATE has the same format as in
             the pack function.  Here's a subroutine that does
             substring:

                 sub substr {
                     local($what,$where,$howmuch) = @_;
                     unpack("x$where a$howmuch", $what);
                 }

             and then there's

                 sub ordinal { unpack("c",$_[0]);  }  #  same  as ord()

             In addition, you may prefix a field with a %<number>
             to indicate that you want a <number>-bit checksum of
             the items instead of the items themselves.  Default
             is a 16-bit checksum.  For example, the following
             computes the same number as the System V sum
             program:

		 while (<>) {
		     $checksum += unpack("%16C*", $_);
		 }
		 $checksum %= 65536;

	     The following efficiently counts the number of set
	     bits in a bit vector:

		 $setbits = unpack("%32b*', $selectmask);

     untie VARIABLE
             Breaks the binding between a variable and a package.
             (See tie().)

     unshift ARRAY,LIST
             Does the opposite of a shift.  Or the opposite of a
             push, depending on how you look at it.  Prepends
             list to the front of the array, and returns the new
             number of elements in the array.

                 unshift(ARGV, '-e') unless $ARGV[0] =~ /^-/;

             Note the LIST is prepended whole, not one element at
             a time, so the prepended elements stay in the same
             order.  Use reverse to do the reverse.

     use Module LIST

     use Module
             Imports some semantics into the current package from
             the named module, generally by aliasing certain
             subroutine or variable names into your package.  It
             is exactly equivalent to

                 BEGIN { require Module; import Module LIST; }

             If you don't want your namespace altered, use
             require instead.

             The BEGIN forces the require and import to happen at
             compile time.  The require makes sure the module is
             loaded into memory if it hasn't been yet.  The
             import is not a builtin--it's just an ordinary
             static method call into the "Module" package to tell
             the module to import the list of features back into
             the current package.  The module can implement its
             import method any way it likes, though most modules
             just choose to derive their import method via
             inheritance from the Exporter class that is defined
             in the Exporter module.

	     Becaue this is wide-open interface,  pragmas
	     (compiler directives) are also implemented this way.
	     Currenlty implemented pragmas are:

		 use integer;
		 use sigtrap qw(SEGV BUS);
		 use strict  qw(subs vars refs);
		 use subs    qw(afunc blurfl);
	
	     These pseudomodules import semantics into the
	     currentl block scope, unlike ordinary modules, which
             import symbols into the current package (which are
             effective through the end of the file).

             There's a corresponding "no" command that unimports
             meanings imported by use.

                 no integer;
                 no strict 'refs';

             See the perlmod manpage for a list of standard
             modules and pragmas.

     utime LIST
             Changes the access and modification times on each
             file of a list of files.  The first two elements of
             the list must be the NUMERICAL access and
             modification times, in that order.  Returns the
             number of files successfully changed.  The inode
             modification time of each file is set to the current
             time.  Example of a "touch" command:

                 #!/usr/bin/perl
                 $now = time;
                 utime $now, $now, @ARGV;


     values ASSOC_ARRAY
             Returns a normal array consisting of all the values
             of the named associative array.  (In a scalar
             context, returns the number of values.)  The values
             are returned in an apparently random order, but it
             is the same order as either the keys() or each()
             function would produce on the same array.  See also
             keys() and each().

     vec EXPR,OFFSET,BITS
             Treats a string as a vector of unsigned integers,
             and returns the value of the bitfield specified.
             May also be assigned to.  BITS must be a power of
             two from 1 to 32.

	     Vectors  created  with vec() can also be manipulated
	     with the logical operators |, & and ^, which will
	     assume a bit vector operation is desired when both
	     operands are strings.

	     To transform a bit vector into a string or array of
	     0's and 1', use these:
		 
		 $bits = unpack("b*", $vector);
		 @bits = split(//, unpack("b*"' $vector));

             If you know the exact length in bits, it can be used
             in place of the *.

     wait    Waits for a child process to terminate and returns
             the pid of the deceased process, or -1 if there are
             no child processes.  The status is returned in $?.

     waitpid PID,FLAGS
             Waits for a particular child process to terminate
             and returns the pid of the deceased process, or -1
             if there is no such child process.  The status is
             returned in $?.  If you say

                 use POSIX "wait_h";
                 ...
                 waitpid(-1,&WNOHANG);

             then you can do a non-blocking wait for any process.
             Non-blocking wait is only available on machines
             supporting either the waitpid(2) or wait4(2) system
             calls.  However, waiting for a particular pid with
             FLAGS of 0 is implemented everywhere.  (Perl
             emulates the system call by remembering the status
             values of processes that have exited but have not
             been harvested by the Perl script yet.)

     wantarray
             Returns TRUE if the context of the currently
             executing subroutine is looking for a list value.
             Returns FALSE if the context is looking for a
             scalar.

                 return wantarray ? () : undef;


     warn LIST
             Produces a message on STDERR just like die(), but
             doesn't exit or throw an exception.

     write FILEHANDLE

     write EXPR

     write   Writes a formatted record (possibly multi-line) to
	     the specified file, using the format associated iwth
	     that file.  By default the format for a file is the
	     one having the same name is the filehandle, but the
	     format for the current output channel, (see the
	     select() function) may be set explicityly by
	     assigning the name of the format to the $~ variable.
	
	     Top of the form processing is handled automatically; if	     
             there is insufficient room on the current page for
             the formatted record, the page is advanced by
             writing a form feed, a special top-of-page format is
             used to format the new page header, and then the
             record is written.  By default the top-of-page
             format is the name of the filehandle with "_TOP"
             appended, but it may be dynamically set to the
             format of your choice by assigning the name to the
             $^ variable while the filehandle is selected.  The
             number of lines remaining on the current page is in
             variable $-, which can be set to 0 to force a new
             page.

             If FILEHANDLE is unspecified, output goes to the
             current default output channel, which starts out as
             STDOUT but may be changed by the select operator.
             If the FILEHANDLE is an EXPR, then the expression is
             evaluated and the resulting string is used to look
             up the name of the FILEHANDLE at run time.  For more
             on formats, see the perlform manpage.

             Note that write is NOT the opposite of read.
             Unfortunately.

     y///    The translation operator.  See the section on tr///
             in the perlop manpage.


 

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