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.


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


     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
     perlboot            Perl OO tutorial for beginners
     perltoot            Perl OO tutorial, part 1
     perltooc            Perl OO tutorial, part 2
     perlbot             Perl OO tricks and examples
     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
     perlrun             Perl execution and options
     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
     perlunifaq          Perl Unicode FAQ
     perluniprops        Index of Unicode Version 5.2.0 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
     perlcompile         Perl compiler suite intro
     perlfilter          Perl source filters
     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
     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
     perlpolicy          Perl development policies
     perlrepository      Perl source repository


     perlbook            Perl book information
     perlcommunity       Perl community information
     perltodo            Perl things to do
     perldoc             Look up Perl documentation in Pod format
     perlhist            Perl history records
     perldelta           Perl changes since previous version
     perl5121delta       Perl changes in version 5.12.1
     perl5120delta       Perl changes in version 5.12.0
     perl5115delta       Perl changes in version 5.11.5
     perl5114delta       Perl changes in version 5.11.4
     perl5113delta       Perl changes in version 5.11.3
     perl5112delta       Perl changes in version 5.11.2
     perl5111delta       Perl changes in version 5.11.1
     perl5110delta       Perl changes in version 5.11.0
     perl5101delta       Perl changes in version 5.10.1
     perl5100delta       Perl changes in version 5.10.0
     perl595delta        Perl changes in version 5.9.5
     perl594delta        Perl changes in version 5.9.4
     perl593delta        Perl changes in version 5.9.3
     perl592delta        Perl changes in version 5.9.2
     perl591delta        Perl changes in version 5.9.1
     perl590delta        Perl changes in version 5.9.0
     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
     perl573delta        Perl changes in version 5.7.3
     perl572delta        Perl changes in version 5.7.2
     perl571delta        Perl changes in version 5.7.1
     perl570delta        Perl changes in version 5.7.0
     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
     perlartistic        Perl Artistic License
     perlgpl             GNU General Public License


     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)


     perlaix             Perl notes for AIX
     perlamiga           Perl notes for AmigaOS
     perlapollo          Perl notes for Apollo DomainOS
     perlbeos            Perl notes for BeOS
     perlbs2000          Perl notes for POSIX-BC BS2000
     perlce              Perl notes for WinCE
     perlcygwin          Perl notes for Cygwin
     perldgux            Perl notes for DG/UX
     perldos             Perl notes for DOS
     perlepoc            Perl notes for EPOC
     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
     perlmpeix           Perl notes for MPE/iX
     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
     perltru64           Perl notes for Tru64
     perluts             Perl notes for UTS
     perlvmesa           Perl notes for VM/ESA
     perlvms             Perl notes for VMS
     perlvos             Perl notes for Stratus VOS
     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:

modularity and reusability using innumerable modules

Described in perlmod, perlmodlib, and perlmodinstall.

embeddable and extensible

Described in perlembed, perlxstut, perlxs, perlcall, perlguts, and xsubpp.

roll-your-own magic variables (including multiple simultaneous DBM implementations)

Described in perltie and AnyDBM_File.

subroutines can now be overridden, autoloaded, and prototyped

Described in perlsub.

arbitrarily nested data structures and anonymous functions

Described in perlreftut, perlref, perldsc, and perllol.

object-oriented programming

Described in perlobj, perlboot, perltoot, perltooc, and perlbot.

support for light-weight processes (threads)

Described in perlthrtut and threads.

support for Unicode, internationalization, and localization

Described in perluniintro, perllocale and Locale::Maketext.

lexical scoping

Described in perlsub.

regular expression enhancements

Described in perlre, with additional examples in perlop.

enhanced debugger and interactive Perl environment, with integrated editor support

Described in perldebtut, perldebug and perldebguts.

POSIX 1003.1 compliant library

Described in POSIX.

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 .


  "@INC"                 locations of perl libraries


  a2p    awk to perl translator
  s2p    sed to perl translator       the Perl homepage       Perl articles (O'Reilly)       the Comprehensive Perl Archive         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.