Perl 5 version 8.8 documentation



perl - Practical Extraction and Report Language


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] ] [ -P ] [ -S ] [ -x[dir] ] [ -i[extension] ] [ -e 'command' ] [ -- ] [ programfile ] [ argument ]...

If you're new to Perl, you should start with perlintro, which is a general intro for beginners and provides some background to help you navigate the rest of Perl's extensive documentation.

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. perlstyle Perl style guide
  11. perlcheat Perl cheat sheet
  12. perltrap Perl traps for the unwary
  13. perldebtut Perl debugging tutorial
  14. perlfaq Perl frequently asked questions
  15. perlfaq1 General Questions About Perl
  16. perlfaq2 Obtaining and Learning about Perl
  17. perlfaq3 Programming Tools
  18. perlfaq4 Data Manipulation
  19. perlfaq5 Files and Formats
  20. perlfaq6 Regexes
  21. perlfaq7 Perl Language Issues
  22. perlfaq8 System Interaction
  23. 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. perlreref Perl regular expressions quick reference
  17. perlref Perl references, the rest of the story
  18. perlform Perl formats
  19. perlobj Perl objects
  20. perltie Perl objects hidden behind simple variables
  21. perldbmfilter Perl DBM filters
  22. perlipc Perl interprocess communication
  23. perlfork Perl fork() information
  24. perlnumber Perl number semantics
  25. perlthrtut Perl threads tutorial
  26. perlothrtut Old Perl threads tutorial
  27. perlport Perl portability guide
  28. perllocale Perl locale support
  29. perluniintro Perl Unicode introduction
  30. perlunicode Perl Unicode support
  31. perlebcdic Considerations for running Perl on EBCDIC platforms
  32. perlsec Perl security
  33. perlmod Perl modules: how they work
  34. perlmodlib Perl modules: how to write and use
  35. perlmodstyle Perl modules: how to write modules with style
  36. perlmodinstall Perl modules: how to install from CPAN
  37. perlnewmod Perl modules: preparing a new module for distribution
  38. perlutil utilities packaged with the Perl distribution
  39. perlcompile Perl compiler suite intro
  40. perlfilter Perl source filters
  41. 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. perlapi Perl API listing (autogenerated)
  9. perlintern Perl internal functions (autogenerated)
  10. perliol C API for Perl's implementation of IO in Layers
  11. perlapio Perl internal IO abstraction interface
  12. perlhack Perl hackers guide


  1. perlbook Perl book information
  2. perltodo Perl things to do
  3. perldoc Look up Perl documentation in Pod format
  4. perlhist Perl history records
  5. perldelta Perl changes since previous version
  6. perl587delta Perl changes in version 5.8.7
  7. perl586delta Perl changes in version 5.8.6
  8. perl585delta Perl changes in version 5.8.5
  9. perl584delta Perl changes in version 5.8.4
  10. perl583delta Perl changes in version 5.8.3
  11. perl582delta Perl changes in version 5.8.2
  12. perl581delta Perl changes in version 5.8.1
  13. perl58delta Perl changes in version 5.8.0
  14. perl573delta Perl changes in version 5.7.3
  15. perl572delta Perl changes in version 5.7.2
  16. perl571delta Perl changes in version 5.7.1
  17. perl570delta Perl changes in version 5.7.0
  18. perl561delta Perl changes in version 5.6.1
  19. perl56delta Perl changes in version 5.6
  20. perl5005delta Perl changes in version 5.005
  21. perl5004delta Perl changes in version 5.004
  22. perlartistic Perl Artistic License
  23. 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. perlhpux Perl notes for HP-UX
  13. perlhurd Perl notes for Hurd
  14. perlirix Perl notes for Irix
  15. perllinux Perl notes for Linux
  16. perlmachten Perl notes for Power MachTen
  17. perlmacos Perl notes for Mac OS (Classic)
  18. perlmacosx Perl notes for Mac OS X
  19. perlmint Perl notes for MiNT
  20. perlmpeix Perl notes for MPE/iX
  21. perlnetware Perl notes for NetWare
  22. perlopenbsd Perl notes for OpenBSD
  23. perlos2 Perl notes for OS/2
  24. perlos390 Perl notes for OS/390
  25. perlos400 Perl notes for OS/400
  26. perlplan9 Perl notes for Plan 9
  27. perlqnx Perl notes for QNX
  28. perlsolaris Perl notes for Solaris
  29. perltru64 Perl notes for Tru64
  30. perluts Perl notes for UTS
  31. perlvmesa Perl notes for VM/ESA
  32. perlvms Perl notes for VMS
  33. perlvos Perl notes for Stratus VOS
  34. perlwin32 Perl notes for Windows

By default, the manpages listed above are installed in the /usr/local/man/ directory.

Extensive additional documentation for Perl modules is available. The default configuration for perl will place this additional documentation in the /usr/local/lib/perl5/man directory (or else in the man subdirectory of the Perl library directory). Some of this additional documentation is distributed standard with Perl, but you'll also find documentation for third-party modules there.

You should be able to view Perl's documentation with your man(1) program by including the proper directories in the appropriate start-up files, or in the MANPATH environment variable. To find out where the configuration has installed the manpages, type:

  1. perl -V:man.dir

If the directories have a common stem, such as /usr/local/man/man1 and /usr/local/man/man3, you need only to add that stem (/usr/local/man) to your man(1) configuration files or your MANPATH environment variable. If they do not share a stem, you'll have to add both stems.

If that doesn't work for some reason, you can still use the supplied perldoc script to view module information. You might also look into getting a replacement man program.

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 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.


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