1PERLRUN(1) Perl Programmers Reference Guide PERLRUN(1)
2
6 perlrun - how to execute the Perl interpreter
7
9 perl [ -sTtuUWX ] [ -hv ] [ -V[:configvar] ]
10 [ -cw ] [ -d[t][:debugger] ] [ -D[number/list] ]
11 [ -pna ] [ -Fpattern ] [ -l[octal] ] [ -0[octal/hexadecimal] ]
12 [ -Idir ] [ -m[-]module ] [ -M[-]'module...' ] [ -f ]
13 [ -C [number/list] ] [ -S ] [ -x[dir] ]
14 [ -i[extension] ]
15 [ [-e|-E] 'command' ] [ -- ] [ programfile ] [ argument ]...
16
18 The normal way to run a Perl program is by making it directly
19 executable, or else by passing the name of the source file as an
20 argument on the command line. (An interactive Perl environment is also
21 possible--see perldebug for details on how to do that.) Upon startup,
22 Perl looks for your program in one of the following places:
23 1. Specified line by line via -e or -E switches on the command line.
25 2. Contained in the file specified by the first filename on the
27 command line. (Note that systems supporting the "#!" notation
28 invoke interpreters this way. See "Location of Perl".)
29 3. Passed in implicitly via standard input. This works only if there
31 are no filename arguments--to pass arguments to a STDIN-read
32 program you must explicitly specify a "-" for the program name.
33 With methods 2 and 3, Perl starts parsing the input file from the
35 beginning, unless you've specified a -x switch, in which case it scans
36 for the first line starting with "#!" and containing the word "perl",
37 and starts there instead. This is useful for running a program
38 embedded in a larger message. (In this case you would indicate the end
39 of the program using the "__END__" token.)
40 The "#!" line is always examined for switches as the line is being
42 parsed. Thus, if you're on a machine that allows only one argument
43 with the "#!" line, or worse, doesn't even recognize the "#!" line, you
44 still can get consistent switch behaviour regardless of how Perl was
45 invoked, even if -x was used to find the beginning of the program.
46 Because historically some operating systems silently chopped off kernel
48 interpretation of the "#!" line after 32 characters, some switches may
49 be passed in on the command line, and some may not; you could even get
50 a "-" without its letter, if you're not careful. You probably want to
51 make sure that all your switches fall either before or after that
52 32-character boundary. Most switches don't actually care if they're
53 processed redundantly, but getting a "-" instead of a complete switch
54 could cause Perl to try to execute standard input instead of your
55 program. And a partial -I switch could also cause odd results.
56 Some switches do care if they are processed twice, for instance
58 combinations of -l and -0. Either put all the switches after the
59 32-character boundary (if applicable), or replace the use of -0digits
60 by "BEGIN{ $/ = "\0digits"; }".
61 Parsing of the "#!" switches starts wherever "perl" is mentioned in the
63 line. The sequences "-*" and "- " are specifically ignored so that you
64 could, if you were so inclined, say
65 #!/bin/sh
67 #! -*-perl-*-
68 eval 'exec perl -x -wS $0 ${1+"$@"}'
69 if 0;
70 to let Perl see the -p switch.
72 A similar trick involves the env program, if you have it.
74 #!/usr/bin/env perl
76 The examples above use a relative path to the perl interpreter, getting
78 whatever version is first in the user's path. If you want a specific
79 version of Perl, say, perl5.14.1, you should place that directly in the
80 "#!" line's path.
81 If the "#!" line does not contain the word "perl" nor the word "indir",
83 the program named after the "#!" is executed instead of the Perl
84 interpreter. This is slightly bizarre, but it helps people on machines
85 that don't do "#!", because they can tell a program that their SHELL is
86 /usr/bin/perl, and Perl will then dispatch the program to the correct
87 interpreter for them.
88 After locating your program, Perl compiles the entire program to an
90 internal form. If there are any compilation errors, execution of the
91 program is not attempted. (This is unlike the typical shell script,
92 which might run part-way through before finding a syntax error.)
93 If the program is syntactically correct, it is executed. If the
95 program runs off the end without hitting an exit() or die() operator,
96 an implicit exit(0) is provided to indicate successful completion.
97 #! and quoting on non-Unix systems
99 Unix's "#!" technique can be simulated on other systems:
100 OS/2
102 Put
103 extproc perl -S -your_switches
105 as the first line in "*.cmd" file (-S due to a bug in cmd.exe's
107 `extproc' handling).
108 MS-DOS
110 Create a batch file to run your program, and codify it in
111 "ALTERNATE_SHEBANG" (see the dosish.h file in the source
112 distribution for more information).
113 Win95/NT
115 The Win95/NT installation, when using the ActiveState installer for
116 Perl, will modify the Registry to associate the .pl extension with
117 the perl interpreter. If you install Perl by other means
118 (including building from the sources), you may have to modify the
119 Registry yourself. Note that this means you can no longer tell the
120 difference between an executable Perl program and a Perl library
121 file.
122 VMS Put
124 $ perl -mysw 'f$env("procedure")' 'p1' 'p2' 'p3' 'p4' 'p5' 'p6' 'p7' 'p8' !
126 $ exit++ + ++$status != 0 and $exit = $status = undef;
127 at the top of your program, where -mysw are any command line
129 switches you want to pass to Perl. You can now invoke the program
130 directly, by saying "perl program", or as a DCL procedure, by
131 saying @program (or implicitly via DCL$PATH by just using the name
132 of the program).
133 This incantation is a bit much to remember, but Perl will display
135 it for you if you say "perl "-V:startperl"".
136 Command-interpreters on non-Unix systems have rather different ideas on
138 quoting than Unix shells. You'll need to learn the special characters
139 in your command-interpreter ("*", "\" and """ are common) and how to
140 protect whitespace and these characters to run one-liners (see -e
141 below).
142 On some systems, you may have to change single-quotes to double ones,
144 which you must not do on Unix or Plan 9 systems. You might also have
145 to change a single % to a %%.
146 For example:
148 # Unix
150 perl -e 'print "Hello world\n"'
151 # MS-DOS, etc.
153 perl -e "print \"Hello world\n\""
154 # VMS
156 perl -e "print ""Hello world\n"""
157 The problem is that none of this is reliable: it depends on the command
159 and it is entirely possible neither works. If 4DOS were the command
160 shell, this would probably work better:
161 perl -e "print <Ctrl-x>"Hello world\n<Ctrl-x>""
163 CMD.EXE in Windows NT slipped a lot of standard Unix functionality in
165 when nobody was looking, but just try to find documentation for its
166 quoting rules.
167 There is no general solution to all of this. It's just a mess.
169 Location of Perl
171 It may seem obvious to say, but Perl is useful only when users can
172 easily find it. When possible, it's good for both /usr/bin/perl and
173 /usr/local/bin/perl to be symlinks to the actual binary. If that can't
174 be done, system administrators are strongly encouraged to put (symlinks
175 to) perl and its accompanying utilities into a directory typically
176 found along a user's PATH, or in some other obvious and convenient
177 place.
178 In this documentation, "#!/usr/bin/perl" on the first line of the
180 program will stand in for whatever method works on your system. You
181 are advised to use a specific path if you care about a specific
182 version.
183 #!/usr/local/bin/perl5.14
185 or if you just want to be running at least version, place a statement
187 like this at the top of your program:
188 use 5.014;
190 Command Switches
192 As with all standard commands, a single-character switch may be
193 clustered with the following switch, if any.
194 #!/usr/bin/perl -spi.orig # same as -s -p -i.orig
196 A "--" signals the end of options and disables further option
198 processing. Any arguments after the "--" are treated as filenames and
199 arguments.
200 Switches include:
202 -0[octal/hexadecimal]
204 specifies the input record separator ($/) as an octal or
205 hexadecimal number. If there are no digits, the null character is
206 the separator. Other switches may precede or follow the digits.
207 For example, if you have a version of find which can print
208 filenames terminated by the null character, you can say this:
209 find . -name '*.orig' -print0 | perl -n0e unlink
211 The special value 00 will cause Perl to slurp files in paragraph
213 mode. Any value 0400 or above will cause Perl to slurp files
214 whole, but by convention the value 0777 is the one normally used
215 for this purpose.
216 You can also specify the separator character using hexadecimal
218 notation: -0xHHH..., where the "H" are valid hexadecimal digits.
219 Unlike the octal form, this one may be used to specify any Unicode
220 character, even those beyond 0xFF. So if you really want a record
221 separator of 0777, specify it as -0x1FF. (This means that you
222 cannot use the -x option with a directory name that consists of
223 hexadecimal digits, or else Perl will think you have specified a
224 hex number to -0.)
225 -a turns on autosplit mode when used with a -n or -p. An implicit
227 split command to the @F array is done as the first thing inside
228 the implicit while loop produced by the -n or -p.
229 perl -ane 'print pop(@F), "\n";'
231 is equivalent to
233 while (<>) {
235 @F = split(' ');
236 print pop(@F), "\n";
237 }
238 An alternate delimiter may be specified using -F.
240 -a implicitly sets -n.
242 -C [number/list]
244 The -C flag controls some of the Perl Unicode features.
245 As of 5.8.1, the -C can be followed either by a number or a list
247 of option letters. The letters, their numeric values, and effects
248 are as follows; listing the letters is equal to summing the
249 numbers.
250 I 1 STDIN is assumed to be in UTF-8
252 O 2 STDOUT will be in UTF-8
253 E 4 STDERR will be in UTF-8
254 S 7 I + O + E
255 i 8 UTF-8 is the default PerlIO layer for input streams
256 o 16 UTF-8 is the default PerlIO layer for output streams
257 D 24 i + o
258 A 32 the @ARGV elements are expected to be strings encoded
259 in UTF-8
260 L 64 normally the "IOEioA" are unconditional, the L makes
261 them conditional on the locale environment variables
262 (the LC_ALL, LC_CTYPE, and LANG, in the order of
263 decreasing precedence) -- if the variables indicate
264 UTF-8, then the selected "IOEioA" are in effect
265 a 256 Set ${^UTF8CACHE} to -1, to run the UTF-8 caching
266 code in debugging mode.
267 For example, -COE and -C6 will both turn on UTF-8-ness on both
269 STDOUT and STDERR. Repeating letters is just redundant, not
270 cumulative nor toggling.
271 The "io" options mean that any subsequent open() (or similar I/O
273 operations) in the current file scope will have the ":utf8" PerlIO
274 layer implicitly applied to them, in other words, UTF-8 is
275 expected from any input stream, and UTF-8 is produced to any
276 output stream. This is just the default, with explicit layers in
277 open() and with binmode() one can manipulate streams as usual.
278 -C on its own (not followed by any number or option list), or the
280 empty string "" for the "PERL_UNICODE" environment variable, has
281 the same effect as -CSDL. In other words, the standard I/O
282 handles and the default "open()" layer are UTF-8-fied but only if
283 the locale environment variables indicate a UTF-8 locale. This
284 behaviour follows the implicit (and problematic) UTF-8 behaviour
285 of Perl 5.8.0. (See "UTF-8 no longer default under UTF-8 locales"
286 in perl581delta.)
287 You can use -C0 (or "0" for "PERL_UNICODE") to explicitly disable
289 all the above Unicode features.
290 The read-only magic variable "${^UNICODE}" reflects the numeric
292 value of this setting. This variable is set during Perl startup
293 and is thereafter read-only. If you want runtime effects, use the
294 three-arg open() (see "open" in perlfunc), the two-arg binmode()
295 (see "binmode" in perlfunc), and the "open" pragma (see open).
296 (In Perls earlier than 5.8.1 the -C switch was a Win32-only switch
298 that enabled the use of Unicode-aware "wide system call" Win32
299 APIs. This feature was practically unused, however, and the
300 command line switch was therefore "recycled".)
301 Note: Since perl 5.10.1, if the -C option is used on the "#!"
303 line, it must be specified on the command line as well, since the
304 standard streams are already set up at this point in the execution
305 of the perl interpreter. You can also use binmode() to set the
306 encoding of an I/O stream.
307 -c causes Perl to check the syntax of the program and then exit
309 without executing it. Actually, it will execute any "BEGIN",
310 "UNITCHECK", or "CHECK" blocks and any "use" statements: these are
311 considered as occurring outside the execution of your program.
312 "INIT" and "END" blocks, however, will be skipped.
313 -d
315 -dt runs the program under the Perl debugger. See perldebug. If t is
316 specified, it indicates to the debugger that threads will be used
317 in the code being debugged.
318 -d:MOD[=bar,baz]
320 -dt:MOD[=bar,baz]
321 runs the program under the control of a debugging, profiling, or
322 tracing module installed as "Devel::MOD". E.g., -d:DProf executes
323 the program using the "Devel::DProf" profiler. As with the -M
324 flag, options may be passed to the "Devel::MOD" package where they
325 will be received and interpreted by the "Devel::MOD::import"
326 routine. Again, like -M, use --d:-MOD to call
327 "Devel::MOD::unimport" instead of import. The comma-separated
328 list of options must follow a "=" character. If t is specified,
329 it indicates to the debugger that threads will be used in the code
330 being debugged. See perldebug.
331 -Dletters
333 -Dnumber
334 sets debugging flags. This switch is enabled only if your perl
335 binary has been built with debugging enabled: normal production
336 perls won't have been.
337 For example, to watch how perl executes your program, use -Dtls.
339 Another nice value is -Dx, which lists your compiled syntax tree,
340 and -Dr displays compiled regular expressions; the format of the
341 output is explained in perldebguts.
342 As an alternative, specify a number instead of list of letters
344 (e.g., -D14 is equivalent to -Dtls):
345 1 p Tokenizing and parsing (with v, displays parse
347 stack)
348 2 s Stack snapshots (with v, displays all stacks)
349 4 l Context (loop) stack processing
350 8 t Trace execution
351 16 o Method and overloading resolution
352 32 c String/numeric conversions
353 64 P Print profiling info, source file input state
354 128 m Memory and SV allocation
355 256 f Format processing
356 512 r Regular expression parsing and execution
357 1024 x Syntax tree dump
358 2048 u Tainting checks
359 4096 U Unofficial, User hacking (reserved for private,
360 unreleased use)
361 8192 H Hash dump -- usurps values()
362 16384 X Scratchpad allocation
363 32768 D Cleaning up
364 65536 S Op slab allocation
365 131072 T Tokenizing
366 262144 R Include reference counts of dumped variables
367 (eg when using -Ds)
368 524288 J show s,t,P-debug (don't Jump over) on opcodes within
369 package DB
370 1048576 v Verbose: use in conjunction with other flags
371 2097152 C Copy On Write
372 4194304 A Consistency checks on internal structures
373 8388608 q quiet - currently only suppresses the "EXECUTING"
374 message
375 16777216 M trace smart match resolution
376 33554432 B dump suBroutine definitions, including special
377 Blocks like BEGIN
378 67108864 L trace Locale-related info; what gets output is very
379 subject to change
380 134217728 i trace PerlIO layer processing. Set PERLIO_DEBUG to
381 the filename to trace to.
382 All these flags require -DDEBUGGING when you compile the Perl
384 executable (but see ":opd" in Devel::Peek or "'debug' mode" in re
385 which may change this). See the INSTALL file in the Perl source
386 distribution for how to do this.
387 If you're just trying to get a print out of each line of Perl code
389 as it executes, the way that "sh -x" provides for shell scripts,
390 you can't use Perl's -D switch. Instead do this
391 # If you have "env" utility
393 env PERLDB_OPTS="NonStop=1 AutoTrace=1 frame=2" perl -dS program
394 # Bourne shell syntax
396 $ PERLDB_OPTS="NonStop=1 AutoTrace=1 frame=2" perl -dS program
397 # csh syntax
399 % (setenv PERLDB_OPTS "NonStop=1 AutoTrace=1 frame=2"; perl -dS program)
400 See perldebug for details and variations.
402 -e commandline
404 may be used to enter one line of program. If -e is given, Perl
405 will not look for a filename in the argument list. Multiple -e
406 commands may be given to build up a multi-line script. Make sure
407 to use semicolons where you would in a normal program.
408 -E commandline
410 behaves just like -e, except that it implicitly enables all
411 optional features (in the main compilation unit). See feature.
412 -f Disable executing $Config{sitelib}/sitecustomize.pl at startup.
414 Perl can be built so that it by default will try to execute
416 $Config{sitelib}/sitecustomize.pl at startup (in a BEGIN block).
417 This is a hook that allows the sysadmin to customize how Perl
418 behaves. It can for instance be used to add entries to the @INC
419 array to make Perl find modules in non-standard locations.
420 Perl actually inserts the following code:
422 BEGIN {
424 do { local $!; -f "$Config{sitelib}/sitecustomize.pl"; }
425 && do "$Config{sitelib}/sitecustomize.pl";
426 }
427 Since it is an actual "do" (not a "require"), sitecustomize.pl
429 doesn't need to return a true value. The code is run in package
430 "main", in its own lexical scope. However, if the script dies, $@
431 will not be set.
432 The value of $Config{sitelib} is also determined in C code and not
434 read from "Config.pm", which is not loaded.
435 The code is executed very early. For example, any changes made to
437 @INC will show up in the output of `perl -V`. Of course, "END"
438 blocks will be likewise executed very late.
439 To determine at runtime if this capability has been compiled in
441 your perl, you can check the value of $Config{usesitecustomize}.
442 -Fpattern
444 specifies the pattern to split on for -a. The pattern may be
445 surrounded by "//", "", or '', otherwise it will be put in single
446 quotes. You can't use literal whitespace or NUL characters in the
447 pattern.
448 -F implicitly sets both -a and -n.
450 -h prints a summary of the options.
452 -i[extension]
454 specifies that files processed by the "<>" construct are to be
455 edited in-place. It does this by renaming the input file, opening
456 the output file by the original name, and selecting that output
457 file as the default for print() statements. The extension, if
458 supplied, is used to modify the name of the old file to make a
459 backup copy, following these rules:
460 If no extension is supplied, and your system supports it, the
462 original file is kept open without a name while the output is
463 redirected to a new file with the original filename. When perl
464 exits, cleanly or not, the original file is unlinked.
465 If the extension doesn't contain a "*", then it is appended to the
467 end of the current filename as a suffix. If the extension does
468 contain one or more "*" characters, then each "*" is replaced with
469 the current filename. In Perl terms, you could think of this as:
470 ($backup = $extension) =~ s/\*/$file_name/g;
472 This allows you to add a prefix to the backup file, instead of (or
474 in addition to) a suffix:
475 $ perl -pi'orig_*' -e 's/bar/baz/' fileA # backup to
477 # 'orig_fileA'
478 Or even to place backup copies of the original files into another
480 directory (provided the directory already exists):
481 $ perl -pi'old/*.orig' -e 's/bar/baz/' fileA # backup to
483 # 'old/fileA.orig'
484 These sets of one-liners are equivalent:
486 $ perl -pi -e 's/bar/baz/' fileA # overwrite current file
488 $ perl -pi'*' -e 's/bar/baz/' fileA # overwrite current file
489 $ perl -pi'.orig' -e 's/bar/baz/' fileA # backup to 'fileA.orig'
491 $ perl -pi'*.orig' -e 's/bar/baz/' fileA # backup to 'fileA.orig'
492 From the shell, saying
494 $ perl -p -i.orig -e "s/foo/bar/; ... "
496 is the same as using the program:
498 #!/usr/bin/perl -pi.orig
500 s/foo/bar/;
501 which is equivalent to
503 #!/usr/bin/perl
505 $extension = '.orig';
506 LINE: while (<>) {
507 if ($ARGV ne $oldargv) {
508 if ($extension !~ /\*/) {
509 $backup = $ARGV . $extension;
510 }
511 else {
512 ($backup = $extension) =~ s/\*/$ARGV/g;
513 }
514 rename($ARGV, $backup);
515 open(ARGVOUT, ">$ARGV");
516 select(ARGVOUT);
517 $oldargv = $ARGV;
518 }
519 s/foo/bar/;
520 }
521 continue {
522 print; # this prints to original filename
523 }
524 select(STDOUT);
525 except that the -i form doesn't need to compare $ARGV to $oldargv
527 to know when the filename has changed. It does, however, use
528 ARGVOUT for the selected filehandle. Note that STDOUT is restored
529 as the default output filehandle after the loop.
530 As shown above, Perl creates the backup file whether or not any
532 output is actually changed. So this is just a fancy way to copy
533 files:
534 $ perl -p -i'/some/file/path/*' -e 1 file1 file2 file3...
536 or
537 $ perl -p -i'.orig' -e 1 file1 file2 file3...
538 You can use "eof" without parentheses to locate the end of each
540 input file, in case you want to append to each file, or reset line
541 numbering (see example in "eof" in perlfunc).
542 If, for a given file, Perl is unable to create the backup file as
544 specified in the extension then it will skip that file and
545 continue on with the next one (if it exists).
546 For a discussion of issues surrounding file permissions and -i,
548 see "Why does Perl let me delete read-only files? Why does -i
549 clobber protected files? Isn't this a bug in Perl?" in perlfaq5.
550 You cannot use -i to create directories or to strip extensions
552 from files.
553 Perl does not expand "~" in filenames, which is good, since some
555 folks use it for their backup files:
556 $ perl -pi~ -e 's/foo/bar/' file1 file2 file3...
558 Note that because -i renames or deletes the original file before
560 creating a new file of the same name, Unix-style soft and hard
561 links will not be preserved.
562 Finally, the -i switch does not impede execution when no files are
564 given on the command line. In this case, no backup is made (the
565 original file cannot, of course, be determined) and processing
566 proceeds from STDIN to STDOUT as might be expected.
567 -Idirectory
569 Directories specified by -I are prepended to the search path for
570 modules (@INC).
571 -l[octnum]
573 enables automatic line-ending processing. It has two separate
574 effects. First, it automatically chomps $/ (the input record
575 separator) when used with -n or -p. Second, it assigns "$\" (the
576 output record separator) to have the value of octnum so that any
577 print statements will have that separator added back on. If
578 octnum is omitted, sets "$\" to the current value of $/. For
579 instance, to trim lines to 80 columns:
580 perl -lpe 'substr($_, 80) = ""'
582 Note that the assignment "$\ = $/" is done when the switch is
584 processed, so the input record separator can be different than the
585 output record separator if the -l switch is followed by a -0
586 switch:
587 gnufind / -print0 | perl -ln0e 'print "found $_" if -p'
589 This sets "$\" to newline and then sets $/ to the null character.
591 -m[-]module
593 -M[-]module
594 -M[-]'module ...'
595 -[mM][-]module=arg[,arg]...
596 -mmodule executes "use" module "();" before executing your
597 program.
598 -Mmodule executes "use" module ";" before executing your program.
600 You can use quotes to add extra code after the module name, e.g.,
601 '-MMODULE qw(foo bar)'.
602 If the first character after the -M or -m is a dash (-) then the
604 'use' is replaced with 'no'.
605 A little builtin syntactic sugar means you can also say
607 -mMODULE=foo,bar or -MMODULE=foo,bar as a shortcut for '-MMODULE
608 qw(foo bar)'. This avoids the need to use quotes when importing
609 symbols. The actual code generated by -MMODULE=foo,bar is "use
610 module split(/,/,q{foo,bar})". Note that the "=" form removes the
611 distinction between -m and -M; that is, -mMODULE=foo,bar is the
612 same as -MMODULE=foo,bar.
613 A consequence of this is that -MMODULE=number never does a version
615 check, unless "MODULE::import()" itself is set up to do a version
616 check, which could happen for example if MODULE inherits from
617 Exporter.
618 -n causes Perl to assume the following loop around your program,
620 which makes it iterate over filename arguments somewhat like sed
621 -n or awk:
622 LINE:
624 while (<>) {
625 ... # your program goes here
626 }
627 Note that the lines are not printed by default. See "-p" to have
629 lines printed. If a file named by an argument cannot be opened
630 for some reason, Perl warns you about it and moves on to the next
631 file.
632 Also note that "<>" passes command line arguments to "open" in
634 perlfunc, which doesn't necessarily interpret them as file names.
635 See perlop for possible security implications.
636 Here is an efficient way to delete all files that haven't been
638 modified for at least a week:
639 find . -mtime +7 -print | perl -nle unlink
641 This is faster than using the -exec switch of find because you
643 don't have to start a process on every filename found (but it's
644 not faster than using the -delete switch available in newer
645 versions of find. It does suffer from the bug of mishandling
646 newlines in pathnames, which you can fix if you follow the example
647 under -0.
648 "BEGIN" and "END" blocks may be used to capture control before or
650 after the implicit program loop, just as in awk.
651 -p causes Perl to assume the following loop around your program,
653 which makes it iterate over filename arguments somewhat like sed:
654 LINE:
656 while (<>) {
657 ... # your program goes here
658 } continue {
659 print or die "-p destination: $!\n";
660 }
661 If a file named by an argument cannot be opened for some reason,
663 Perl warns you about it, and moves on to the next file. Note that
664 the lines are printed automatically. An error occurring during
665 printing is treated as fatal. To suppress printing use the -n
666 switch. A -p overrides a -n switch.
667 "BEGIN" and "END" blocks may be used to capture control before or
669 after the implicit loop, just as in awk.
670 -s enables rudimentary switch parsing for switches on the command
672 line after the program name but before any filename arguments (or
673 before an argument of --). Any switch found there is removed from
674 @ARGV and sets the corresponding variable in the Perl program.
675 The following program prints "1" if the program is invoked with a
676 -xyz switch, and "abc" if it is invoked with -xyz=abc.
677 #!/usr/bin/perl -s
679 if ($xyz) { print "$xyz\n" }
680 Do note that a switch like --help creates the variable "${-help}",
682 which is not compliant with "use strict "refs"". Also, when using
683 this option on a script with warnings enabled you may get a lot of
684 spurious "used only once" warnings.
685 -S makes Perl use the PATH environment variable to search for the
687 program unless the name of the program contains path separators.
688 On some platforms, this also makes Perl append suffixes to the
690 filename while searching for it. For example, on Win32 platforms,
691 the ".bat" and ".cmd" suffixes are appended if a lookup for the
692 original name fails, and if the name does not already end in one
693 of those suffixes. If your Perl was compiled with "DEBUGGING"
694 turned on, using the -Dp switch to Perl shows how the search
695 progresses.
696 Typically this is used to emulate "#!" startup on platforms that
698 don't support "#!". It's also convenient when debugging a script
699 that uses "#!", and is thus normally found by the shell's $PATH
700 search mechanism.
701 This example works on many platforms that have a shell compatible
703 with Bourne shell:
704 #!/usr/bin/perl
706 eval 'exec /usr/bin/perl -wS $0 ${1+"$@"}'
707 if $running_under_some_shell;
708 The system ignores the first line and feeds the program to
710 /bin/sh, which proceeds to try to execute the Perl program as a
711 shell script. The shell executes the second line as a normal
712 shell command, and thus starts up the Perl interpreter. On some
713 systems $0 doesn't always contain the full pathname, so the -S
714 tells Perl to search for the program if necessary. After Perl
715 locates the program, it parses the lines and ignores them because
716 the variable $running_under_some_shell is never true. If the
717 program will be interpreted by csh, you will need to replace
718 "${1+"$@"}" with $*, even though that doesn't understand embedded
719 spaces (and such) in the argument list. To start up sh rather
720 than csh, some systems may have to replace the "#!" line with a
721 line containing just a colon, which will be politely ignored by
722 Perl. Other systems can't control that, and need a totally
723 devious construct that will work under any of csh, sh, or Perl,
724 such as the following:
725 eval '(exit $?0)' && eval 'exec perl -wS $0 ${1+"$@"}'
727 & eval 'exec /usr/bin/perl -wS $0 $argv:q'
728 if $running_under_some_shell;
729 If the filename supplied contains directory separators (and so is
731 an absolute or relative pathname), and if that file is not found,
732 platforms that append file extensions will do so and try to look
733 for the file with those extensions added, one by one.
734 On DOS-like platforms, if the program does not contain directory
736 separators, it will first be searched for in the current directory
737 before being searched for on the PATH. On Unix platforms, the
738 program will be searched for strictly on the PATH.
739 -t Like -T, but taint checks will issue warnings rather than fatal
741 errors. These warnings can now be controlled normally with "no
742 warnings qw(taint)".
743 Note: This is not a substitute for "-T"! This is meant to be used
745 only as a temporary development aid while securing legacy code:
746 for real production code and for new secure code written from
747 scratch, always use the real -T.
748 -T turns on "taint" so you can test them. Ordinarily these checks
750 are done only when running setuid or setgid. It's a good idea to
751 turn them on explicitly for programs that run on behalf of someone
752 else whom you might not necessarily trust, such as CGI programs or
753 any internet servers you might write in Perl. See perlsec for
754 details. For security reasons, this option must be seen by Perl
755 quite early; usually this means it must appear early on the
756 command line or in the "#!" line for systems which support that
757 construct.
758 -u This switch causes Perl to dump core after compiling your program.
760 You can then in theory take this core dump and turn it into an
761 executable file by using the undump program (not supplied). This
762 speeds startup at the expense of some disk space (which you can
763 minimize by stripping the executable). (Still, a "hello world"
764 executable comes out to about 200K on my machine.) If you want to
765 execute a portion of your program before dumping, use the dump()
766 operator instead. Note: availability of undump is platform
767 specific and may not be available for a specific port of Perl.
768 -U allows Perl to do unsafe operations. Currently the only "unsafe"
770 operations are attempting to unlink directories while running as
771 superuser and running setuid programs with fatal taint checks
772 turned into warnings. Note that warnings must be enabled along
773 with this option to actually generate the taint-check warnings.
774 -v prints the version and patchlevel of your perl executable.
776 -V prints summary of the major perl configuration values and the
778 current values of @INC.
779 -V:configvar
781 Prints to STDOUT the value of the named configuration variable(s),
782 with multiples when your "configvar" argument looks like a regex
783 (has non-letters). For example:
784 $ perl -V:libc
786 libc='/lib/libc-2.2.4.so';
787 $ perl -V:lib.
788 libs='-lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc';
789 libc='/lib/libc-2.2.4.so';
790 $ perl -V:lib.*
791 libpth='/usr/local/lib /lib /usr/lib';
792 libs='-lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc';
793 lib_ext='.a';
794 libc='/lib/libc-2.2.4.so';
795 libperl='libperl.a';
796 ....
797 Additionally, extra colons can be used to control formatting. A
799 trailing colon suppresses the linefeed and terminator ";",
800 allowing you to embed queries into shell commands. (mnemonic:
801 PATH separator ":".)
802 $ echo "compression-vars: " `perl -V:z.*: ` " are here !"
804 compression-vars: zcat='' zip='zip' are here !
805 A leading colon removes the "name=" part of the response, this
807 allows you to map to the name you need. (mnemonic: empty label)
808 $ echo "goodvfork="`./perl -Ilib -V::usevfork`
810 goodvfork=false;
811 Leading and trailing colons can be used together if you need
813 positional parameter values without the names. Note that in the
814 case below, the "PERL_API" params are returned in alphabetical
815 order.
816 $ echo building_on `perl -V::osname: -V::PERL_API_.*:` now
818 building_on 'linux' '5' '1' '9' now
819 -w prints warnings about dubious constructs, such as variable names
821 mentioned only once and scalar variables used before being set;
822 redefined subroutines; references to undefined filehandles;
823 filehandles opened read-only that you are attempting to write on;
824 values used as a number that don't look like numbers; using an
825 array as though it were a scalar; if your subroutines recurse more
826 than 100 deep; and innumerable other things.
827 This switch really just enables the global $^W variable; normally,
829 the lexically scoped "use warnings" pragma is preferred. You can
830 disable or promote into fatal errors specific warnings using
831 "__WARN__" hooks, as described in perlvar and "warn" in perlfunc.
832 See also perldiag and perltrap. A fine-grained warning facility
833 is also available if you want to manipulate entire classes of
834 warnings; see warnings.
835 -W Enables all warnings regardless of "no warnings" or $^W. See
837 warnings.
838 -X Disables all warnings regardless of "use warnings" or $^W. See
840 warnings.
841 -x
843 -xdirectory
844 tells Perl that the program is embedded in a larger chunk of
845 unrelated text, such as in a mail message. Leading garbage will
846 be discarded until the first line that starts with "#!" and
847 contains the string "perl". Any meaningful switches on that line
848 will be applied.
849 All references to line numbers by the program (warnings, errors,
851 ...) will treat the "#!" line as the first line. Thus a warning
852 on the 2nd line of the program, which is on the 100th line in the
853 file will be reported as line 2, not as line 100. This can be
854 overridden by using the "#line" directive. (See "Plain Old
855 Comments (Not!)" in perlsyn)
856 If a directory name is specified, Perl will switch to that
858 directory before running the program. The -x switch controls only
859 the disposal of leading garbage. The program must be terminated
860 with "__END__" if there is trailing garbage to be ignored; the
861 program can process any or all of the trailing garbage via the
862 "DATA" filehandle if desired.
863 The directory, if specified, must appear immediately following the
865 -x with no intervening whitespace.
866
868 HOME Used if "chdir" has no argument.
869 LOGDIR Used if "chdir" has no argument and HOME is not set.
871 PATH Used in executing subprocesses, and in finding the program
873 if -S is used.
874 PERL5LIB A list of directories in which to look for Perl library
876 files before looking in the standard library. Any
877 architecture-specific and version-specific directories,
878 such as version/archname/, version/, or archname/ under the
879 specified locations are automatically included if they
880 exist, with this lookup done at interpreter startup time.
881 In addition, any directories matching the entries in
882 $Config{inc_version_list} are added. (These typically
883 would be for older compatible perl versions installed in
884 the same directory tree.)
885 If PERL5LIB is not defined, PERLLIB is used. Directories
887 are separated (like in PATH) by a colon on Unixish
888 platforms and by a semicolon on Windows (the proper path
889 separator being given by the command "perl -V:path_sep").
890 When running taint checks, either because the program was
892 running setuid or setgid, or the -T or -t switch was
893 specified, neither PERL5LIB nor PERLLIB is consulted. The
894 program should instead say:
895 use lib "/my/directory";
897 PERL5OPT Command-line options (switches). Switches in this variable
899 are treated as if they were on every Perl command line.
900 Only the -[CDIMUdmtwW] switches are allowed. When running
901 taint checks (either because the program was running setuid
902 or setgid, or because the -T or -t switch was used), this
903 variable is ignored. If PERL5OPT begins with -T, tainting
904 will be enabled and subsequent options ignored. If
905 PERL5OPT begins with -t, tainting will be enabled, a
906 writable dot removed from @INC, and subsequent options
907 honored.
908 PERLIO A space (or colon) separated list of PerlIO layers. If perl
910 is built to use PerlIO system for IO (the default) these
911 layers affect Perl's IO.
912 It is conventional to start layer names with a colon (for
914 example, ":perlio") to emphasize their similarity to
915 variable "attributes". But the code that parses layer
916 specification strings, which is also used to decode the
917 PERLIO environment variable, treats the colon as a
918 separator.
919 An unset or empty PERLIO is equivalent to the default set
921 of layers for your platform; for example, ":unix:perlio" on
922 Unix-like systems and ":unix:crlf" on Windows and other
923 DOS-like systems.
924 The list becomes the default for all Perl's IO.
926 Consequently only built-in layers can appear in this list,
927 as external layers (such as ":encoding()") need IO in order
928 to load them! See "open pragma" for how to add external
929 encodings as defaults.
930 Layers it makes sense to include in the PERLIO environment
932 variable are briefly summarized below. For more details see
933 PerlIO.
934 :bytes A pseudolayer that turns the ":utf8" flag off for
936 the layer below; unlikely to be useful on its own
937 in the global PERLIO environment variable. You
938 perhaps were thinking of ":crlf:bytes" or
939 ":perlio:bytes".
940 :crlf A layer which does CRLF to "\n" translation
942 distinguishing "text" and "binary" files in the
943 manner of MS-DOS and similar operating systems.
944 (It currently does not mimic MS-DOS as far as
945 treating of Control-Z as being an end-of-file
946 marker.)
947 :mmap A layer that implements "reading" of files by using
949 mmap(2) to make an entire file appear in the
950 process's address space, and then using that as
951 PerlIO's "buffer".
952 :perlio This is a re-implementation of stdio-like buffering
954 written as a PerlIO layer. As such it will call
955 whatever layer is below it for its operations,
956 typically ":unix".
957 :pop An experimental pseudolayer that removes the
959 topmost layer. Use with the same care as is
960 reserved for nitroglycerine.
961 :raw A pseudolayer that manipulates other layers.
963 Applying the ":raw" layer is equivalent to calling
964 "binmode($fh)". It makes the stream pass each byte
965 as-is without translation. In particular, both
966 CRLF translation and intuiting ":utf8" from the
967 locale are disabled.
968 Unlike in earlier versions of Perl, ":raw" is not
970 just the inverse of ":crlf": other layers which
971 would affect the binary nature of the stream are
972 also removed or disabled.
973 :stdio This layer provides a PerlIO interface by wrapping
975 system's ANSI C "stdio" library calls. The layer
976 provides both buffering and IO. Note that the
977 ":stdio" layer does not do CRLF translation even if
978 that is the platform's normal behaviour. You will
979 need a ":crlf" layer above it to do that.
980 :unix Low-level layer that calls "read", "write",
982 "lseek", etc.
983 :utf8 A pseudolayer that enables a flag in the layer
985 below to tell Perl that output should be in utf8
986 and that input should be regarded as already in
987 valid utf8 form. WARNING: It does not check for
988 validity and as such should be handled with extreme
989 caution for input, because security violations can
990 occur with non-shortest UTF-8 encodings, etc.
991 Generally ":encoding(UTF-8)" is the best option
992 when reading UTF-8 encoded data.
993 :win32 On Win32 platforms this experimental layer uses
995 native "handle" IO rather than a Unix-like numeric
996 file descriptor layer. Known to be buggy in this
997 release (5.14).
998 The default set of layers should give acceptable results on
1000 all platforms
1001 For Unix platforms that will be the equivalent of "unix
1003 perlio" or "stdio". Configure is set up to prefer the
1004 "stdio" implementation if the system's library provides for
1005 fast access to the buffer; otherwise, it uses the "unix
1006 perlio" implementation.
1007 On Win32 the default in this release (5.14) is "unix crlf".
1009 Win32's "stdio" has a number of bugs/mis-features for Perl
1010 IO which are somewhat depending on the version and vendor
1011 of the C compiler. Using our own "crlf" layer as the buffer
1012 avoids those issues and makes things more uniform. The
1013 "crlf" layer provides CRLF conversion as well as buffering.
1014 This release (5.14) uses "unix" as the bottom layer on
1016 Win32, and so still uses the C compiler's numeric file
1017 descriptor routines. There is an experimental native
1018 "win32" layer, which is expected to be enhanced and should
1019 eventually become the default under Win32.
1020 The PERLIO environment variable is completely ignored when
1022 Perl is run in taint mode.
1023 PERLIO_DEBUG
1025 If set to the name of a file or device when Perl is run
1026 with the -Di command-line switch, the logging of certain
1027 operations of the PerlIO subsystem will be redirected to
1028 the specified file rather than going to stderr, which is
1029 the default. The file is opened in append mode. Typical
1030 uses are in Unix:
1031 % env PERLIO_DEBUG=/tmp/perlio.log perl -Di script ...
1033 and under Win32, the approximately equivalent:
1035 > set PERLIO_DEBUG=CON
1037 perl -Di script ...
1038 This functionality is disabled for setuid scripts, for
1040 scripts run with -T, and for scripts run on a Perl built
1041 without "-DDEBUGGING" support.
1042 PERLLIB A list of directories in which to look for Perl library
1044 files before looking in the standard library. If PERL5LIB
1045 is defined, PERLLIB is not used.
1046 The PERLLIB environment variable is completely ignored when
1048 Perl is run in taint mode.
1049 PERL5DB The command used to load the debugger code. The default
1051 is:
1052 BEGIN { require "perl5db.pl" }
1054 The PERL5DB environment variable is only used when Perl is
1056 started with a bare -d switch.
1057 PERL5DB_THREADED
1059 If set to a true value, indicates to the debugger that the
1060 code being debugged uses threads.
1061 PERL5SHELL (specific to the Win32 port)
1063 On Win32 ports only, may be set to an alternative shell
1064 that Perl must use internally for executing "backtick"
1065 commands or system(). Default is "cmd.exe /x/d/c" on
1066 WindowsNT and "command.com /c" on Windows95. The value is
1067 considered space-separated. Precede any character that
1068 needs to be protected, like a space or backslash, with
1069 another backslash.
1070 Note that Perl doesn't use COMSPEC for this purpose because
1072 COMSPEC has a high degree of variability among users,
1073 leading to portability concerns. Besides, Perl can use a
1074 shell that may not be fit for interactive use, and setting
1075 COMSPEC to such a shell may interfere with the proper
1076 functioning of other programs (which usually look in
1077 COMSPEC to find a shell fit for interactive use).
1078 Before Perl 5.10.0 and 5.8.8, PERL5SHELL was not taint
1080 checked when running external commands. It is recommended
1081 that you explicitly set (or delete) $ENV{PERL5SHELL} when
1082 running in taint mode under Windows.
1083 PERL_ALLOW_NON_IFS_LSP (specific to the Win32 port)
1085 Set to 1 to allow the use of non-IFS compatible LSPs
1086 (Layered Service Providers). Perl normally searches for an
1087 IFS-compatible LSP because this is required for its
1088 emulation of Windows sockets as real filehandles. However,
1089 this may cause problems if you have a firewall such as
1090 McAfee Guardian, which requires that all applications use
1091 its LSP but which is not IFS-compatible, because clearly
1092 Perl will normally avoid using such an LSP.
1093 Setting this environment variable to 1 means that Perl will
1095 simply use the first suitable LSP enumerated in the
1096 catalog, which keeps McAfee Guardian happy--and in that
1097 particular case Perl still works too because McAfee
1098 Guardian's LSP actually plays other games which allow
1099 applications requiring IFS compatibility to work.
1100 PERL_DEBUG_MSTATS
1102 Relevant only if Perl is compiled with the "malloc"
1103 included with the Perl distribution; that is, if "perl
1104 -V:d_mymalloc" is "define".
1105 If set, this dumps out memory statistics after execution.
1107 If set to an integer greater than one, also dumps out
1108 memory statistics after compilation.
1109 PERL_DESTRUCT_LEVEL
1111 Relevant only if your Perl executable was built with
1112 -DDEBUGGING, this controls the behaviour of global
1113 destruction of objects and other references. See
1114 "PERL_DESTRUCT_LEVEL" in perlhacktips for more information.
1115 PERL_DL_NONLAZY
1117 Set to "1" to have Perl resolve all undefined symbols when
1118 it loads a dynamic library. The default behaviour is to
1119 resolve symbols when they are used. Setting this variable
1120 is useful during testing of extensions, as it ensures that
1121 you get an error on misspelled function names even if the
1122 test suite doesn't call them.
1123 PERL_ENCODING
1125 If using the "use encoding" pragma without an explicit
1126 encoding name, the PERL_ENCODING environment variable is
1127 consulted for an encoding name.
1128 PERL_HASH_SEED
1130 (Since Perl 5.8.1, new semantics in Perl 5.18.0) Used to
1131 override the randomization of Perl's internal hash
1132 function. The value is expressed in hexadecimal, and may
1133 include a leading 0x. Truncated patterns are treated as
1134 though they are suffixed with sufficient 0's as required.
1135 If the option is provided, and "PERL_PERTURB_KEYS" is NOT
1137 set, then a value of '0' implies "PERL_PERTURB_KEYS=0" and
1138 any other value implies "PERL_PERTURB_KEYS=2".
1139 PLEASE NOTE: The hash seed is sensitive information. Hashes
1141 are randomized to protect against local and remote attacks
1142 against Perl code. By manually setting a seed, this
1143 protection may be partially or completely lost.
1144 See "Algorithmic Complexity Attacks" in perlsec,
1146 "PERL_PERTURB_KEYS", and "PERL_HASH_SEED_DEBUG" for more
1147 information.
1148 PERL_PERTURB_KEYS
1150 (Since Perl 5.18.0) Set to "0" or "NO" then traversing
1151 keys will be repeatable from run to run for the same
1152 PERL_HASH_SEED. Insertion into a hash will not change the
1153 order, except to provide for more space in the hash. When
1154 combined with setting PERL_HASH_SEED this mode is as close
1155 to pre 5.18 behavior as you can get.
1156 When set to "1" or "RANDOM" then traversing keys will be
1158 randomized. Every time a hash is inserted into the key
1159 order will change in a random fashion. The order may not be
1160 repeatable in a following program run even if the
1161 PERL_HASH_SEED has been specified. This is the default mode
1162 for perl.
1163 When set to "2" or "DETERMINISTIC" then inserting keys into
1165 a hash will cause the key order to change, but in a way
1166 that is repeatable from program run to program run.
1167 NOTE: Use of this option is considered insecure, and is
1169 intended only for debugging non-deterministic behavior in
1170 Perl's hash function. Do not use it in production.
1171 See "Algorithmic Complexity Attacks" in perlsec and
1173 "PERL_HASH_SEED" and "PERL_HASH_SEED_DEBUG" for more
1174 information. You can get and set the key traversal mask for
1175 a specific hash by using the "hash_traversal_mask()"
1176 function from Hash::Util.
1177 PERL_HASH_SEED_DEBUG
1179 (Since Perl 5.8.1.) Set to "1" to display (to STDERR)
1180 information about the hash function, seed, and what type of
1181 key traversal randomization is in effect at the beginning
1182 of execution. This, combined with "PERL_HASH_SEED" and
1183 "PERL_PERTURB_KEYS" is intended to aid in debugging
1184 nondeterministic behaviour caused by hash randomization.
1185 Note that any information about the hash function,
1187 especially the hash seed is sensitive information: by
1188 knowing it, one can craft a denial-of-service attack
1189 against Perl code, even remotely; see "Algorithmic
1190 Complexity Attacks" in perlsec for more information. Do not
1191 disclose the hash seed to people who don't need to know it.
1192 See also "hash_seed()" and "key_traversal_mask()" in
1193 Hash::Util.
1194 An example output might be:
1196 HASH_FUNCTION = ONE_AT_A_TIME_HARD HASH_SEED = 0x652e9b9349a7a032 PERTURB_KEYS = 1 (RANDOM)
1198 PERL_MEM_LOG
1200 If your Perl was configured with -Accflags=-DPERL_MEM_LOG,
1201 setting the environment variable "PERL_MEM_LOG" enables
1202 logging debug messages. The value has the form
1203 "<number>[m][s][t]", where "number" is the file descriptor
1204 number you want to write to (2 is default), and the
1205 combination of letters specifies that you want information
1206 about (m)emory and/or (s)v, optionally with (t)imestamps.
1207 For example, "PERL_MEM_LOG=1mst" logs all information to
1208 stdout. You can write to other opened file descriptors in a
1209 variety of ways:
1210 $ 3>foo3 PERL_MEM_LOG=3m perl ...
1212 PERL_ROOT (specific to the VMS port)
1214 A translation-concealed rooted logical name that contains
1215 Perl and the logical device for the @INC path on VMS only.
1216 Other logical names that affect Perl on VMS include
1217 PERLSHR, PERL_ENV_TABLES, and SYS$TIMEZONE_DIFFERENTIAL,
1218 but are optional and discussed further in perlvms and in
1219 README.vms in the Perl source distribution.
1220 PERL_SIGNALS
1222 Available in Perls 5.8.1 and later. If set to "unsafe",
1223 the pre-Perl-5.8.0 signal behaviour (which is immediate but
1224 unsafe) is restored. If set to "safe", then safe (but
1225 deferred) signals are used. See "Deferred Signals (Safe
1226 Signals)" in perlipc.
1227 PERL_UNICODE
1229 Equivalent to the -C command-line switch. Note that this
1230 is not a boolean variable. Setting this to "1" is not the
1231 right way to "enable Unicode" (whatever that would mean).
1232 You can use "0" to "disable Unicode", though (or
1233 alternatively unset PERL_UNICODE in your shell before
1234 starting Perl). See the description of the -C switch for
1235 more information.
1236 PERL_USE_UNSAFE_INC
1238 If perl has been configured to not have the current
1239 directory in @INC by default, this variable can be set to
1240 "1" to reinstate it. It's primarily intended for use while
1241 building and testing modules that have not been updated to
1242 deal with "." not being in @INC and should not be set in
1243 the environment for day-to-day use.
1244 SYS$LOGIN (specific to the VMS port)
1246 Used if chdir has no argument and HOME and LOGDIR are not
1247 set.
1248 Perl also has environment variables that control how Perl handles data
1250 specific to particular natural languages; see perllocale.
1251 Perl and its various modules and components, including its test
1253 frameworks, may sometimes make use of certain other environment
1254 variables. Some of these are specific to a particular platform.
1255 Please consult the appropriate module documentation and any
1256 documentation for your platform (like perlsolaris, perllinux,
1257 perlmacosx, perlwin32, etc) for variables peculiar to those specific
1258 situations.
1259 Perl makes all environment variables available to the program being
1261 executed, and passes these along to any child processes it starts.
1262 However, programs running setuid would do well to execute the following
1263 lines before doing anything else, just to keep people honest:
1264 $ENV{PATH} = "/bin:/usr/bin"; # or whatever you need
1266 $ENV{SHELL} = "/bin/sh" if exists $ENV{SHELL};
1267 delete @ENV{qw(IFS CDPATH ENV BASH_ENV)};
1268perl v5.26.3 2018-03-23 PERLRUN(1)