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Perl 5 version 12.2 documentation
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perl - The Perl language interpreter


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 ]...


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

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.


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


  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. perlboot Perl OO tutorial for beginners
  7. perltoot Perl OO tutorial, part 1
  8. perltooc Perl OO tutorial, part 2
  9. perlbot Perl OO tricks and examples
  10. perlperf Perl Performance and Optimization Techniques
  11. perlstyle Perl style guide
  12. perlcheat Perl cheat sheet
  13. perltrap Perl traps for the unwary
  14. perldebtut Perl debugging tutorial
  15. perlfaq Perl frequently asked questions
  16. perlfaq1 General Questions About Perl
  17. perlfaq2 Obtaining and Learning about Perl
  18. perlfaq3 Programming Tools
  19. perlfaq4 Data Manipulation
  20. perlfaq5 Files and Formats
  21. perlfaq6 Regexes
  22. perlfaq7 Perl Language Issues
  23. perlfaq8 System Interaction
  24. 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. perlrun Perl execution and options
  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 Version 5.2.0 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. perlcompile Perl compiler suite intro
  45. perlfilter Perl source filters
  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. perlclib Internal replacements for standard C library functions
  6. perlguts Perl internal functions for those doing extensions
  7. perlcall Perl calling conventions from C
  8. perlmroapi Perl method resolution plugin interface
  9. perlreapi Perl regular expression plugin interface
  10. perlreguts Perl regular expression engine internals
  11. perlapi Perl API listing (autogenerated)
  12. perlintern Perl internal functions (autogenerated)
  13. perliol C API for Perl's implementation of IO in Layers
  14. perlapio Perl internal IO abstraction interface
  15. perlhack Perl hackers guide
  16. perlpolicy Perl development policies
  17. perlrepository Perl source repository


  1. perlbook Perl book information
  2. perlcommunity Perl community information
  3. perltodo Perl things to do
  4. perldoc Look up Perl documentation in Pod format
  5. perlhist Perl history records
  6. perldelta Perl changes since previous version
  7. perl5121delta Perl changes in version 5.12.1
  8. perl5120delta Perl changes in version 5.12.0
  9. perl5115delta Perl changes in version 5.11.5
  10. perl5114delta Perl changes in version 5.11.4
  11. perl5113delta Perl changes in version 5.11.3
  12. perl5112delta Perl changes in version 5.11.2
  13. perl5111delta Perl changes in version 5.11.1
  14. perl5110delta Perl changes in version 5.11.0
  15. perl5101delta Perl changes in version 5.10.1
  16. perl5100delta Perl changes in version 5.10.0
  17. perl595delta Perl changes in version 5.9.5
  18. perl594delta Perl changes in version 5.9.4
  19. perl593delta Perl changes in version 5.9.3
  20. perl592delta Perl changes in version 5.9.2
  21. perl591delta Perl changes in version 5.9.1
  22. perl590delta Perl changes in version 5.9.0
  23. perl589delta Perl changes in version 5.8.9
  24. perl588delta Perl changes in version 5.8.8
  25. perl587delta Perl changes in version 5.8.7
  26. perl586delta Perl changes in version 5.8.6
  27. perl585delta Perl changes in version 5.8.5
  28. perl584delta Perl changes in version 5.8.4
  29. perl583delta Perl changes in version 5.8.3
  30. perl582delta Perl changes in version 5.8.2
  31. perl581delta Perl changes in version 5.8.1
  32. perl58delta Perl changes in version 5.8.0
  33. perl573delta Perl changes in version 5.7.3
  34. perl572delta Perl changes in version 5.7.2
  35. perl571delta Perl changes in version 5.7.1
  36. perl570delta Perl changes in version 5.7.0
  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. perlartistic Perl Artistic License
  42. perlgpl GNU General Public License


  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)


  1. perlaix Perl notes for AIX
  2. perlamiga Perl notes for AmigaOS
  3. perlapollo Perl notes for Apollo DomainOS
  4. perlbeos Perl notes for BeOS
  5. perlbs2000 Perl notes for POSIX-BC BS2000
  6. perlce Perl notes for WinCE
  7. perlcygwin Perl notes for Cygwin
  8. perldgux Perl notes for DG/UX
  9. perldos Perl notes for DOS
  10. perlepoc Perl notes for EPOC
  11. perlfreebsd Perl notes for FreeBSD
  12. perlhaiku Perl notes for Haiku
  13. perlhpux Perl notes for HP-UX
  14. perlhurd Perl notes for Hurd
  15. perlirix Perl notes for Irix
  16. perllinux Perl notes for Linux
  17. perlmacos Perl notes for Mac OS (Classic)
  18. perlmacosx Perl notes for Mac OS X
  19. perlmpeix Perl notes for MPE/iX
  20. perlnetware Perl notes for NetWare
  21. perlopenbsd Perl notes for OpenBSD
  22. perlos2 Perl notes for OS/2
  23. perlos390 Perl notes for OS/390
  24. perlos400 Perl notes for OS/400
  25. perlplan9 Perl notes for Plan 9
  26. perlqnx Perl notes for QNX
  27. perlriscos Perl notes for RISC OS
  28. perlsolaris Perl notes for Solaris
  29. perlsymbian Perl notes for Symbian
  30. perltru64 Perl notes for Tru64
  31. perluts Perl notes for UTS
  32. perlvmesa Perl notes for VM/ESA
  33. perlvms Perl notes for VMS
  34. perlvos Perl notes for Stratus VOS
  35. perlwin32 Perl notes for Windows

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

In general, if something strange has gone wrong with your program and you're not sure where you should look for help, try the -w switch first. It will often point out exactly where the trouble is.


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

Perl is a language optimized for scanning arbitrary text files, extracting information from those text files, and printing reports based on that information. It's also a good language for many system management tasks. The language is intended to be practical (easy to use, efficient, complete) rather than beautiful (tiny, elegant, minimal).

Perl combines (in the author's opinion, anyway) some of the best features of C, sed, awk, and sh, so people familiar with those languages should have little difficulty with it. (Language historians will also note some vestiges of csh, Pascal, and even BASIC-PLUS.) Expression syntax corresponds closely to C expression syntax. Unlike most Unix utilities, Perl does not arbitrarily limit the size of your data--if you've got the memory, Perl can slurp in your whole file as a single string. Recursion is of unlimited depth. And the tables used by hashes (sometimes called "associative arrays") grow as necessary to prevent degraded performance. Perl can use sophisticated pattern matching techniques to scan large amounts of data quickly. Although optimized for scanning text, Perl can also deal with binary data, and can make dbm files look like hashes. Setuid Perl scripts are safer than C programs through a dataflow tracing mechanism that prevents many stupid security holes.

If you have a problem that would ordinarily use sed or awk or sh, but it exceeds their capabilities or must run a little faster, and you don't want to write the silly thing in C, then Perl may be for you. There are also translators to turn your sed and awk scripts into Perl scripts.

But wait, there's more...

Begun in 1993 (see perlhist), Perl version 5 is nearly a complete rewrite that provides the following additional benefits:

Okay, that's definitely enough hype.


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


See perlrun.


Larry Wall <>, 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 .


  1. "@INC" locations of perl libraries


  1. a2p awk to perl translator
  2. s2p sed to perl translator
  3. the Perl homepage
  4. Perl articles (O'Reilly)
  5. the Comprehensive Perl Archive
  6. the Perl Mongers


The use warnings pragma (and the -w switch) produces some lovely diagnostics.

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 -w switch?


The -w switch 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 . 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.


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.