Perl 5 version 22.4 documentation

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
  5.     perlrequick 	Perl regular expressions quick start
  6.     perlretut		Perl regular expressions tutorial
  8.     perlootut		Perl OO tutorial for beginners
  10.     perlperf		Perl Performance and Optimization Techniques
  12.     perlstyle		Perl style guide
  14.     perlcheat		Perl cheat sheet
  15.     perltrap		Perl traps for the unwary
  16.     perldebtut		Perl debugging tutorial
  18.     perlfaq		Perl frequently asked questions
  19.       perlfaq1		General Questions About Perl
  20.       perlfaq2		Obtaining and Learning about Perl
  21.       perlfaq3		Programming Tools
  22.       perlfaq4		Data Manipulation
  23.       perlfaq5		Files and Formats
  24.       perlfaq6		Regexes
  25.       perlfaq7		Perl Language Issues
  26.       perlfaq8		System Interaction
  27.       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
  25.     perlipc		Perl interprocess communication
  26.     perlfork		Perl fork() information
  27.     perlnumber		Perl number semantics
  29.     perlthrtut		Perl threads tutorial
  31.     perlport		Perl portability guide
  32.     perllocale		Perl locale support
  33.     perluniintro	Perl Unicode introduction
  34.     perlunicode 	Perl Unicode support
  35.     perlunicook 	Perl Unicode cookbook
  36.     perlunifaq		Perl Unicode FAQ
  37.     perluniprops	Index of Unicode properties in Perl
  38.     perlunitut		Perl Unicode tutorial
  39.     perlebcdic		Considerations for running Perl on EBCDIC platforms
  41.     perlsec		Perl security
  43.     perlmod		Perl modules: how they work
  44.     perlmodlib		Perl modules: how to write and use
  45.     perlmodstyle	Perl modules: how to write modules with style
  46.     perlmodinstall	Perl modules: how to install from CPAN
  47.     perlnewmod		Perl modules: preparing a new module for distribution
  48.     perlpragma		Perl modules: writing a user pragma
  50.     perlutil		utilities packaged with the Perl distribution
  52.     perlfilter		Perl source filters
  54.     perldtrace		Perl's support for DTrace
  56.     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
  13.     perlapi		Perl API listing (autogenerated)
  14.     perlintern		Perl internal functions (autogenerated)
  15.     perliol		C API for Perl's implementation of IO in Layers
  16.     perlapio		Perl internal IO abstraction interface
  18.     perlhack		Perl hackers guide
  19.     perlsource		Guide to the Perl source tree
  20.     perlinterp		Overview of the Perl interpreter source and how it works
  21.     perlhacktut 	Walk through the creation of a simple C code patch
  22.     perlhacktips	Tips for Perl core C code hacking
  23.     perlpolicy		Perl development policies
  24.     perlgit		Using git with the Perl repository

Miscellaneous

  1.     perlbook		Perl book information
  2.     perlcommunity	Perl community information
  4.     perldoc		Look up Perl documentation in Pod format
  6.     perlhist		Perl history records
  7.     perldelta		Perl changes since previous version
  8.     perl5223delta	Perl changes in version 5.22.3
  9.     perl5222delta	Perl changes in version 5.22.2
  10.     perl5221delta	Perl changes in version 5.22.1
  11.     perl5220delta	Perl changes in version 5.22.0
  12.     perl5203delta	Perl changes in version 5.20.3
  13.     perl5202delta	Perl changes in version 5.20.2
  14.     perl5201delta	Perl changes in version 5.20.1
  15.     perl5200delta	Perl changes in version 5.20.0
  16.     perl5184delta	Perl changes in version 5.18.4
  17.     perl5182delta	Perl changes in version 5.18.2
  18.     perl5181delta	Perl changes in version 5.18.1
  19.     perl5180delta	Perl changes in version 5.18.0
  20.     perl5163delta	Perl changes in version 5.16.3
  21.     perl5162delta	Perl changes in version 5.16.2
  22.     perl5161delta	Perl changes in version 5.16.1
  23.     perl5160delta	Perl changes in version 5.16.0
  24.     perl5144delta	Perl changes in version 5.14.4
  25.     perl5143delta	Perl changes in version 5.14.3
  26.     perl5142delta	Perl changes in version 5.14.2
  27.     perl5141delta	Perl changes in version 5.14.1
  28.     perl5140delta	Perl changes in version 5.14.0
  29.     perl5125delta	Perl changes in version 5.12.5
  30.     perl5124delta	Perl changes in version 5.12.4
  31.     perl5123delta	Perl changes in version 5.12.3
  32.     perl5122delta	Perl changes in version 5.12.2
  33.     perl5121delta	Perl changes in version 5.12.1
  34.     perl5120delta	Perl changes in version 5.12.0
  35.     perl5101delta	Perl changes in version 5.10.1
  36.     perl5100delta	Perl changes in version 5.10.0
  37.     perl589delta	Perl changes in version 5.8.9
  38.     perl588delta	Perl changes in version 5.8.8
  39.     perl587delta	Perl changes in version 5.8.7
  40.     perl586delta	Perl changes in version 5.8.6
  41.     perl585delta	Perl changes in version 5.8.5
  42.     perl584delta	Perl changes in version 5.8.4
  43.     perl583delta	Perl changes in version 5.8.3
  44.     perl582delta	Perl changes in version 5.8.2
  45.     perl581delta	Perl changes in version 5.8.1
  46.     perl58delta 	Perl changes in version 5.8.0
  47.     perl561delta	Perl changes in version 5.6.1
  48.     perl56delta 	Perl changes in version 5.6
  49.     perl5005delta	Perl changes in version 5.005
  50.     perl5004delta	Perl changes in version 5.004
  52.     perlexperiment	A listing of experimental features in Perl
  54.     perlartistic	Perl Artistic License
  55.     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.