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# perl

Perl 5 version 22.0 documentation
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# perl

- NAME
- SYNOPSIS
- GETTING HELP
  - Overview
  - Tutorials
  - Reference Manual
  - Internals and C Language Interface
  - Miscellaneous
  - Language-Specific
  - Platform-Specific
  - Stubs for Deleted Documents
- DESCRIPTION
- AVAILABILITY
- ENVIRONMENT
- AUTHOR
- FILES
- SEE ALSO
- DIAGNOSTICS
- BUGS
- NOTES

# NAME

perl - The Perl 5 language interpreter

# SYNOPSIS

perl [ -sTtuUWX ] [ -hv ] [ -V[:configvar] ] [ -cw ] [ -d[t][:debugger] ] [ -D[number/list] ] [ -pna ] [ -Fpattern ] [ -l[octal] ] [ -0[octal/hexadecimal] ] [ -Idir ] [ -m[-]module ] [ -M[-]'module...' ] [ -f ] [ -C [number/list] ] [ -S ] [ -x[dir] ] [ -i[extension] ] [ [-e|-E] 'command' ] [ -- ] [ programfile ] [ argument ]...

For more information on these options, you can run `perldoc perlrun` .

# GETTING HELP

The perldoc program gives you access to all the documentation that comes with Perl. You can get more documentation, tutorials and community support online at http://www.perl.org/.

If you're new to Perl, you should start by running `perldoc perlintro` , which is a general intro for beginners and provides some background to help you navigate the rest of Perl's extensive documentation. Run `perldoc perldoc` to learn more things you can do with perldoc.

For ease of access, the Perl manual has been split up into several sections.

## Overview

        perl		Perl overview (this section)    perlintro		Perl introduction for beginners    perlrun		Perl execution and options    perltoc		Perl documentation table of contents

## Tutorials

        perlreftut		Perl references short introduction    perldsc		Perl data structures intro    perllol		Perl data structures: arrays of arrays    perlrequick 	Perl regular expressions quick start    perlretut		Perl regular expressions tutorial    perlootut		Perl OO tutorial for beginners    perlperf		Perl Performance and Optimization Techniques    perlstyle		Perl style guide    perlcheat		Perl cheat sheet    perltrap		Perl traps for the unwary    perldebtut		Perl debugging tutorial    perlfaq		Perl frequently asked questions      perlfaq1		General Questions About Perl      perlfaq2		Obtaining and Learning about Perl      perlfaq3		Programming Tools      perlfaq4		Data Manipulation      perlfaq5		Files and Formats      perlfaq6		Regexes      perlfaq7		Perl Language Issues      perlfaq8		System Interaction      perlfaq9		Networking

## Reference Manual

        perlsyn		Perl syntax    perldata		Perl data structures    perlop		Perl operators and precedence    perlsub		Perl subroutines    perlfunc		Perl built-in functions      perlopentut	Perl open() tutorial      perlpacktut	Perl pack() and unpack() tutorial    perlpod		Perl plain old documentation    perlpodspec 	Perl plain old documentation format specification    perlpodstyle	Perl POD style guide    perldiag		Perl diagnostic messages    perllexwarn 	Perl warnings and their control    perldebug		Perl debugging    perlvar		Perl predefined variables    perlre		Perl regular expressions, the rest of the story    perlrebackslash	Perl regular expression backslash sequences    perlrecharclass	Perl regular expression character classes    perlreref		Perl regular expressions quick reference    perlref		Perl references, the rest of the story    perlform		Perl formats    perlobj		Perl objects    perltie		Perl objects hidden behind simple variables      perldbmfilter	Perl DBM filters    perlipc		Perl interprocess communication    perlfork		Perl fork() information    perlnumber		Perl number semantics    perlthrtut		Perl threads tutorial    perlport		Perl portability guide    perllocale		Perl locale support    perluniintro	Perl Unicode introduction    perlunicode 	Perl Unicode support    perlunicook 	Perl Unicode cookbook    perlunifaq		Perl Unicode FAQ    perluniprops	Index of Unicode properties in Perl    perlunitut		Perl Unicode tutorial    perlebcdic		Considerations for running Perl on EBCDIC platforms    perlsec		Perl security    perlmod		Perl modules: how they work    perlmodlib		Perl modules: how to write and use    perlmodstyle	Perl modules: how to write modules with style    perlmodinstall	Perl modules: how to install from CPAN    perlnewmod		Perl modules: preparing a new module for distribution    perlpragma		Perl modules: writing a user pragma    perlutil		utilities packaged with the Perl distribution    perlfilter		Perl source filters    perldtrace		Perl's support for DTrace    perlglossary	Perl Glossary

## Internals and C Language Interface

        perlembed		Perl ways to embed perl in your C or C++ application    perldebguts 	Perl debugging guts and tips    perlxstut		Perl XS tutorial    perlxs		Perl XS application programming interface    perlxstypemap	Perl XS C/Perl type conversion tools    perlclib		Internal replacements for standard C library functions    perlguts		Perl internal functions for those doing extensions    perlcall		Perl calling conventions from C    perlmroapi		Perl method resolution plugin interface    perlreapi		Perl regular expression plugin interface    perlreguts		Perl regular expression engine internals    perlapi		Perl API listing (autogenerated)    perlintern		Perl internal functions (autogenerated)    perliol		C API for Perl's implementation of IO in Layers    perlapio		Perl internal IO abstraction interface    perlhack		Perl hackers guide    perlsource		Guide to the Perl source tree    perlinterp		Overview of the Perl interpreter source and how it works    perlhacktut 	Walk through the creation of a simple C code patch    perlhacktips	Tips for Perl core C code hacking    perlpolicy		Perl development policies    perlgit		Using git with the Perl repository

## Miscellaneous

        perlbook		Perl book information    perlcommunity	Perl community information    perldoc		Look up Perl documentation in Pod format    perlhist		Perl history records    perldelta		Perl changes since previous version    perl52111delta	Perl changes in version 5.21.11    perl52110delta	Perl changes in version 5.21.10    perl5219delta	Perl changes in version 5.21.9    perl5218delta	Perl changes in version 5.21.8    perl5217delta	Perl changes in version 5.21.7    perl5216delta	Perl changes in version 5.21.6    perl5215delta	Perl changes in version 5.21.5    perl5214delta	Perl changes in version 5.21.4    perl5213delta	Perl changes in version 5.21.3    perl5212delta	Perl changes in version 5.21.2    perl5211delta	Perl changes in version 5.21.1    perl5210delta	Perl changes in version 5.21.0    perl5202delta	Perl changes in version 5.20.2    perl5201delta	Perl changes in version 5.20.1    perl5200delta	Perl changes in version 5.20.0    perl5184delta	Perl changes in version 5.18.4    perl5182delta	Perl changes in version 5.18.2    perl5181delta	Perl changes in version 5.18.1    perl5180delta	Perl changes in version 5.18.0    perl5163delta	Perl changes in version 5.16.3    perl5162delta	Perl changes in version 5.16.2    perl5161delta	Perl changes in version 5.16.1    perl5160delta	Perl changes in version 5.16.0    perl5144delta	Perl changes in version 5.14.4    perl5143delta	Perl changes in version 5.14.3    perl5142delta	Perl changes in version 5.14.2    perl5141delta	Perl changes in version 5.14.1    perl5140delta	Perl changes in version 5.14.0    perl5125delta	Perl changes in version 5.12.5    perl5124delta	Perl changes in version 5.12.4    perl5123delta	Perl changes in version 5.12.3    perl5122delta	Perl changes in version 5.12.2    perl5121delta	Perl changes in version 5.12.1    perl5120delta	Perl changes in version 5.12.0    perl5101delta	Perl changes in version 5.10.1    perl5100delta	Perl changes in version 5.10.0    perl589delta	Perl changes in version 5.8.9    perl588delta	Perl changes in version 5.8.8    perl587delta	Perl changes in version 5.8.7    perl586delta	Perl changes in version 5.8.6    perl585delta	Perl changes in version 5.8.5    perl584delta	Perl changes in version 5.8.4    perl583delta	Perl changes in version 5.8.3    perl582delta	Perl changes in version 5.8.2    perl581delta	Perl changes in version 5.8.1    perl58delta 	Perl changes in version 5.8.0    perl561delta	Perl changes in version 5.6.1    perl56delta 	Perl changes in version 5.6    perl5005delta	Perl changes in version 5.005    perl5004delta	Perl changes in version 5.004    perlexperiment	A listing of experimental features in Perl    perlartistic	Perl Artistic License    perlgpl		GNU General Public License

## Language-Specific

        perlcn		Perl for Simplified Chinese (in EUC-CN)    perljp		Perl for Japanese (in EUC-JP)    perlko		Perl for Korean (in EUC-KR)    perltw		Perl for Traditional Chinese (in Big5)

## Platform-Specific

        perlaix		Perl notes for AIX    perlamiga		Perl notes for AmigaOS    perlandroid		Perl notes for Android    perlbs2000		Perl notes for POSIX-BC BS2000    perlce		Perl notes for WinCE    perlcygwin		Perl notes for Cygwin    perldos		Perl notes for DOS    perlfreebsd 	Perl notes for FreeBSD    perlhaiku		Perl notes for Haiku    perlhpux		Perl notes for HP-UX    perlhurd		Perl notes for Hurd    perlirix		Perl notes for Irix    perllinux		Perl notes for Linux    perlmacos		Perl notes for Mac OS (Classic)    perlmacosx		Perl notes for Mac OS X    perlnetware 	Perl notes for NetWare    perlopenbsd 	Perl notes for OpenBSD    perlos2		Perl notes for OS/2    perlos390		Perl notes for OS/390    perlos400		Perl notes for OS/400    perlplan9		Perl notes for Plan 9    perlqnx		Perl notes for QNX    perlriscos		Perl notes for RISC OS    perlsolaris 	Perl notes for Solaris    perlsymbian 	Perl notes for Symbian    perlsynology 	Perl notes for Synology    perltru64		Perl notes for Tru64    perlvms		Perl notes for VMS    perlvos		Perl notes for Stratus VOS    perlwin32		Perl notes for Windows

## Stubs for Deleted Documents

        perlboot		    perlbot		    perlrepository    perltodo    perltooc		    perltoot

On a Unix-like system, these documentation files will usually also be available as manpages for use with the man program.

Some documentation is not available as man pages, so if a cross-reference is not found by man, try it with perldoc. Perldoc can also take you directly to documentation for functions (with the -f switch). See `perldoc --help` (or `perldoc perldoc` or `man perldoc` ) for other helpful options perldoc has to offer.

In general, if something strange has gone wrong with your program and you're not sure where you should look for help, try making your code comply with use strict and use warnings. These will often point out exactly where the trouble is.

# DESCRIPTION

Perl officially stands for Practical Extraction and Report Language, except when it doesn't.

Perl was originally a language optimized for scanning arbitrary text files, extracting information from those text files, and printing reports based on that information. It quickly became a good language for many system management tasks. Over the years, Perl has grown into a general-purpose programming language. It's widely used for everything from quick "one-liners" to full-scale application development.

The language is intended to be practical (easy to use, efficient, complete) rather than beautiful (tiny, elegant, minimal). It combines (in the author's opinion, anyway) some of the best features of sed, awk, and sh, making it familiar and easy to use for Unix users to whip up quick solutions to annoying problems. Its general-purpose programming facilities support procedural, functional, and object-oriented programming paradigms, making Perl a comfortable language for the long haul on major projects, whatever your bent.

Perl's roots in text processing haven't been forgotten over the years. It still boasts some of the most powerful regular expressions to be found anywhere, and its support for Unicode text is world-class. It handles all kinds of structured text, too, through an extensive collection of extensions. Those libraries, collected in the CPAN, provide ready-made solutions to an astounding array of problems. When they haven't set the standard themselves, they steal from the best -- just like Perl itself.

# AVAILABILITY

Perl is available for most operating systems, including virtually all Unix-like platforms. See Supported Platforms in perlport for a listing.

# ENVIRONMENT

See perlrun.

# AUTHOR

Larry Wall <larry@wall.org>, with the help of oodles of other folks.

If your Perl success stories and testimonials may be of help to others who wish to advocate the use of Perl in their applications, or if you wish to simply express your gratitude to Larry and the Perl developers, please write to perl-thanks@perl.org .

# FILES

     "@INC"			locations of perl libraries

# SEE ALSO

     http://www.perl.org/       the Perl homepage http://www.perl.com/       Perl articles (O'Reilly) http://www.cpan.org/       the Comprehensive Perl Archive http://www.pm.org/         the Perl Mongers

# DIAGNOSTICS

Using the `use strict` pragma ensures that all variables are properly declared and prevents other misuses of legacy Perl features.

The `use warnings` pragma produces some lovely diagnostics. One can also use the -w flag, but its use is normally discouraged, because it gets applied to all executed Perl code, including that not under your control.

See perldiag for explanations of all Perl's diagnostics. The `use diagnostics` pragma automatically turns Perl's normally terse warnings and errors into these longer forms.

Compilation errors will tell you the line number of the error, with an indication of the next token or token type that was to be examined. (In a script passed to Perl via -e switches, each -e is counted as one line.)

Setuid scripts have additional constraints that can produce error messages such as "Insecure dependency". See perlsec.

Did we mention that you should definitely consider using the use warnings pragma?

# BUGS

The behavior implied by the use warnings pragma is not mandatory.

Perl is at the mercy of your machine's definitions of various operations such as type casting, atof(), and floating-point output with sprintf().

If your stdio requires a seek or eof between reads and writes on a particular stream, so does Perl. (This doesn't apply to sysread() and syswrite().)

While none of the built-in data types have any arbitrary size limits (apart from memory size), there are still a few arbitrary limits: a given variable name may not be longer than 251 characters. Line numbers displayed by diagnostics are internally stored as short integers, so they are limited to a maximum of 65535 (higher numbers usually being affected by wraparound).

You may mail your bug reports (be sure to include full configuration information as output by the myconfig program in the perl source tree, or by `perl -V` ) to perlbug@perl.org . If you've succeeded in compiling perl, the perlbug script in the utils/ subdirectory can be used to help mail in a bug report.

Perl actually stands for Pathologically Eclectic Rubbish Lister, but don't tell anyone I said that.

# NOTES

The Perl motto is "There's more than one way to do it." Divining how many more is left as an exercise to the reader.

The three principal virtues of a programmer are Laziness, Impatience, and Hubris. See the Camel Book for why.

Page index

- NAME
- SYNOPSIS
- GETTING HELP
  - Overview
  - Tutorials
  - Reference Manual
  - Internals and C Language Interface
  - Miscellaneous
  - Language-Specific
  - Platform-Specific
  - Stubs for Deleted Documents
- DESCRIPTION
- AVAILABILITY
- ENVIRONMENT
- AUTHOR
- FILES
- SEE ALSO
- DIAGNOSTICS
- BUGS
- NOTES