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perl

Perl 5 version 20.1 documentation
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perl

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

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

Tutorials

  1. perlreftut Perl references short introduction
  2. perldsc Perl data structures intro
  3. perllol Perl data structures: arrays of arrays
  4. perlrequick Perl regular expressions quick start
  5. perlretut Perl regular expressions tutorial
  6. perlootut Perl OO tutorial for beginners
  7. perlperf Perl Performance and Optimization Techniques
  8. perlstyle Perl style guide
  9. perlcheat Perl cheat sheet
  10. perltrap Perl traps for the unwary
  11. perldebtut Perl debugging tutorial
  12. perlfaq Perl frequently asked questions
  13. perlfaq1 General Questions About Perl
  14. perlfaq2 Obtaining and Learning about Perl
  15. perlfaq3 Programming Tools
  16. perlfaq4 Data Manipulation
  17. perlfaq5 Files and Formats
  18. perlfaq6 Regexes
  19. perlfaq7 Perl Language Issues
  20. perlfaq8 System Interaction
  21. perlfaq9 Networking

Reference Manual

  1. perlsyn Perl syntax
  2. perldata Perl data structures
  3. perlop Perl operators and precedence
  4. perlsub Perl subroutines
  5. perlfunc Perl built-in functions
  6. perlopentut Perl open() tutorial
  7. perlpacktut Perl pack() and unpack() tutorial
  8. perlpod Perl plain old documentation
  9. perlpodspec Perl plain old documentation format specification
  10. perlpodstyle Perl POD style guide
  11. perldiag Perl diagnostic messages
  12. perllexwarn Perl warnings and their control
  13. perldebug Perl debugging
  14. perlvar Perl predefined variables
  15. perlre Perl regular expressions, the rest of the story
  16. perlrebackslash Perl regular expression backslash sequences
  17. perlrecharclass Perl regular expression character classes
  18. perlreref Perl regular expressions quick reference
  19. perlref Perl references, the rest of the story
  20. perlform Perl formats
  21. perlobj Perl objects
  22. perltie Perl objects hidden behind simple variables
  23. perldbmfilter Perl DBM filters
  24. perlipc Perl interprocess communication
  25. perlfork Perl fork() information
  26. perlnumber Perl number semantics
  27. perlthrtut Perl threads tutorial
  28. perlport Perl portability guide
  29. perllocale Perl locale support
  30. perluniintro Perl Unicode introduction
  31. perlunicode Perl Unicode support
  32. perlunifaq Perl Unicode FAQ
  33. perluniprops Index of Unicode properties in Perl
  34. perlunitut Perl Unicode tutorial
  35. perlebcdic Considerations for running Perl on EBCDIC platforms
  36. perlsec Perl security
  37. perlmod Perl modules: how they work
  38. perlmodlib Perl modules: how to write and use
  39. perlmodstyle Perl modules: how to write modules with style
  40. perlmodinstall Perl modules: how to install from CPAN
  41. perlnewmod Perl modules: preparing a new module for distribution
  42. perlpragma Perl modules: writing a user pragma
  43. perlutil utilities packaged with the Perl distribution
  44. perlfilter Perl source filters
  45. perldtrace Perl's support for DTrace
  46. perlglossary Perl Glossary

Internals and C Language Interface

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

Miscellaneous

  1. perlbook Perl book information
  2. perlcommunity Perl community information
  3. perldoc Look up Perl documentation in Pod format
  4. perlhist Perl history records
  5. perldelta Perl changes since previous version
  6. perl5200delta Perl changes in version 5.20.0
  7. perl5182delta Perl changes in version 5.18.2
  8. perl5181delta Perl changes in version 5.18.1
  9. perl5180delta Perl changes in version 5.18.0
  10. perl5161delta Perl changes in version 5.16.1
  11. perl5162delta Perl changes in version 5.16.2
  12. perl5163delta Perl changes in version 5.16.3
  13. perl5160delta Perl changes in version 5.16.0
  14. perl5144delta Perl changes in version 5.14.4
  15. perl5143delta Perl changes in version 5.14.3
  16. perl5142delta Perl changes in version 5.14.2
  17. perl5141delta Perl changes in version 5.14.1
  18. perl5140delta Perl changes in version 5.14.0
  19. perl5125delta Perl changes in version 5.12.5
  20. perl5124delta Perl changes in version 5.12.4
  21. perl5123delta Perl changes in version 5.12.3
  22. perl5122delta Perl changes in version 5.12.2
  23. perl5121delta Perl changes in version 5.12.1
  24. perl5120delta Perl changes in version 5.12.0
  25. perl5101delta Perl changes in version 5.10.1
  26. perl5100delta Perl changes in version 5.10.0
  27. perl589delta Perl changes in version 5.8.9
  28. perl588delta Perl changes in version 5.8.8
  29. perl587delta Perl changes in version 5.8.7
  30. perl586delta Perl changes in version 5.8.6
  31. perl585delta Perl changes in version 5.8.5
  32. perl584delta Perl changes in version 5.8.4
  33. perl583delta Perl changes in version 5.8.3
  34. perl582delta Perl changes in version 5.8.2
  35. perl581delta Perl changes in version 5.8.1
  36. perl58delta Perl changes in version 5.8.0
  37. perl561delta Perl changes in version 5.6.1
  38. perl56delta Perl changes in version 5.6
  39. perl5005delta Perl changes in version 5.005
  40. perl5004delta Perl changes in version 5.004
  41. perlexperiment A listing of experimental features in Perl
  42. perlartistic Perl Artistic License
  43. perlgpl GNU General Public License

Language-Specific

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

Platform-Specific

  1. perlaix Perl notes for AIX
  2. perlamiga Perl notes for AmigaOS
  3. perlandroid Perl notes for Android
  4. perlbs2000 Perl notes for POSIX-BC BS2000
  5. perlce Perl notes for WinCE
  6. perlcygwin Perl notes for Cygwin
  7. perldos Perl notes for DOS
  8. perlfreebsd Perl notes for FreeBSD
  9. perlhaiku Perl notes for Haiku
  10. perlhpux Perl notes for HP-UX
  11. perlhurd Perl notes for Hurd
  12. perlirix Perl notes for Irix
  13. perllinux Perl notes for Linux
  14. perlmacos Perl notes for Mac OS (Classic)
  15. perlmacosx Perl notes for Mac OS X
  16. perlnetware Perl notes for NetWare
  17. perlopenbsd Perl notes for OpenBSD
  18. perlos2 Perl notes for OS/2
  19. perlos390 Perl notes for OS/390
  20. perlos400 Perl notes for OS/400
  21. perlplan9 Perl notes for Plan 9
  22. perlqnx Perl notes for QNX
  23. perlriscos Perl notes for RISC OS
  24. perlsolaris Perl notes for Solaris
  25. perlsymbian Perl notes for Symbian
  26. perlsynology Perl notes for Synology
  27. perltru64 Perl notes for Tru64
  28. perlvms Perl notes for VMS
  29. perlvos Perl notes for Stratus VOS
  30. perlwin32 Perl notes for Windows

Stubs for Deleted Documents

  1. perlboot
  2. perlbot
  3. perlrepository
  4. perltodo
  5. perltooc
  6. 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

  1. "@INC" locations of perl libraries

SEE ALSO

  1. http://www.perl.org/ the Perl homepage
  2. http://www.perl.com/ Perl articles (O'Reilly)
  3. http://www.cpan.org/ the Comprehensive Perl Archive
  4. 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.