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PERL(1) Perl Programmers Reference Guide PERL(1)

perl - The Perl 5 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 ]...

For more information on these options, you can run "perldoc perlrun".

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
    perlrun             Perl execution and options
    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
    perlootut           Perl OO tutorial for beginners
    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

    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
    perldocstyle        Perl style guide for core docs
    perlpodstyle        Perl POD style guide
    perldiag            Perl diagnostic messages
    perldeprecation     Perl deprecations
    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
    perlclass           Perl class syntax
      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
    perlunicook         Perl Unicode cookbook
    perlunifaq          Perl Unicode FAQ
    perluniprops        Index of Unicode properties in Perl
    perlunitut          Perl Unicode tutorial
    perlebcdic          Considerations for running Perl on EBCDIC platforms
    perlsec             Perl security
    perlsecpolicy       Perl security report handling policy
    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
    perlfilter          Perl source filters
    perldtrace          Perl's support for DTrace
    perlglossary        Perl Glossary

    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
    perlxstypemap       Perl XS C/Perl type conversion tools
    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
    perlclassguts       Internals of class syntax
    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
    perlsource          Guide to the Perl source tree
    perlinterp          Overview of the Perl interpreter source and how it works
    perlhacktut         Walk through the creation of a simple C code patch
    perlhacktips        Tips for Perl core C code hacking
    perlpolicy          Perl development policies
    perlgov             Perl Rules of Governance
    perlgit             Using git with the Perl repository

    perlhist            Perl history records
    perldelta           Perl changes since previous version
    perl5381delta       Perl changes in version 5.38.1
    perl5380delta       Perl changes in version 5.38.0
    perl5363delta       Perl changes in version 5.36.3
    perl5362delta       Perl changes in version 5.36.2
    perl5361delta       Perl changes in version 5.36.1
    perl5360delta       Perl changes in version 5.36.0
    perl5343delta       Perl changes in version 5.34.3
    perl5342delta       Perl changes in version 5.34.2
    perl5341delta       Perl changes in version 5.34.1
    perl5340delta       Perl changes in version 5.34.0
    perl5321delta       Perl changes in version 5.32.1
    perl5320delta       Perl changes in version 5.32.0
    perl5303delta       Perl changes in version 5.30.3
    perl5302delta       Perl changes in version 5.30.2
    perl5301delta       Perl changes in version 5.30.1
    perl5300delta       Perl changes in version 5.30.0
    perl5283delta       Perl changes in version 5.28.3
    perl5282delta       Perl changes in version 5.28.2
    perl5281delta       Perl changes in version 5.28.1
    perl5280delta       Perl changes in version 5.28.0
    perl5263delta       Perl changes in version 5.26.3
    perl5262delta       Perl changes in version 5.26.2
    perl5261delta       Perl changes in version 5.26.1
    perl5260delta       Perl changes in version 5.26.0
    perl5244delta       Perl changes in version 5.24.4
    perl5243delta       Perl changes in version 5.24.3
    perl5242delta       Perl changes in version 5.24.2
    perl5241delta       Perl changes in version 5.24.1
    perl5240delta       Perl changes in version 5.24.0
    perl5224delta       Perl changes in version 5.22.4
    perl5223delta       Perl changes in version 5.22.3
    perl5222delta       Perl changes in version 5.22.2
    perl5221delta       Perl changes in version 5.22.1
    perl5220delta       Perl changes in version 5.22.0
    perl5203delta       Perl changes in version 5.20.3
    perl5202delta       Perl changes in version 5.20.2
    perl5201delta       Perl changes in version 5.20.1
    perl5200delta       Perl changes in version 5.20.0
    perl5184delta       Perl changes in version 5.18.4
    perl5182delta       Perl changes in version 5.18.2
    perl5181delta       Perl changes in version 5.18.1
    perl5180delta       Perl changes in version 5.18.0
    perl5163delta       Perl changes in version 5.16.3
    perl5162delta       Perl changes in version 5.16.2
    perl5161delta       Perl changes in version 5.16.1
    perl5160delta       Perl changes in version 5.16.0
    perl5144delta       Perl changes in version 5.14.4
    perl5143delta       Perl changes in version 5.14.3
    perl5142delta       Perl changes in version 5.14.2
    perl5141delta       Perl changes in version 5.14.1
    perl5140delta       Perl changes in version 5.14.0
    perl5125delta       Perl changes in version 5.12.5
    perl5124delta       Perl changes in version 5.12.4
    perl5123delta       Perl changes in version 5.12.3
    perl5122delta       Perl changes in version 5.12.2
    perl5121delta       Perl changes in version 5.12.1
    perl5120delta       Perl changes in version 5.12.0
    perl5101delta       Perl changes in version 5.10.1
    perl5100delta       Perl changes in version 5.10.0
    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
    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

    perlbook            Perl book information
    perlcommunity       Perl community information
    perldoc             Look up Perl documentation in Pod format
    perlexperiment      A listing of experimental features in Perl
    perlartistic        Perl Artistic License
    perlgpl             GNU General Public License

    perlcn              Perl for Simplified Chinese (in UTF-8)
    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
    perlandroid         Perl notes for Android
    perlbs2000          Perl notes for POSIX-BC BS2000
    perlcygwin          Perl notes for Cygwin
    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
    perlmacosx          Perl notes for Mac OS X
    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
    perlsynology        Perl notes for Synology
    perltru64           Perl notes for Tru64
    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.

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.

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.

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

See "ENVIRONMENT" in 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

"@INC" above is a reference to the built-in variable of the same name; see perlvar for more information.       the Perl homepage       Perl articles       the Comprehensive Perl Archive         the Perl Mongers

Using the "use strict" pragma ensures that all variables are properly declared and prevents other misuses of legacy Perl features. These are enabled by default within the scope of "use v5.12" (or higher).

The "use warnings" pragma produces some lovely diagnostics. It is enabled by default when you say "use v5.35" (or higher). 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?

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 submit 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 <>.

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.

2024-05-14 perl v5.38.2