Perl

• NAME
• SYNOPSIS
• Overview
• Tutorials
• Reference Manual
• Internals and C Language Interface
• Miscellaneous
• Language-Specific
• Platform-Specific
• DESCRIPTION
• AVAILABILITY
• ENVIRONMENT
• AUTHOR
• FILES
• SEE ALSO
• DIAGNOSTICS
• BUGS
• NOTES

perl - Practical Extraction and Report Language

perl [ -sTuU ] [ -hv ] [ -V[:configvar] ] [ -cw ] [ -d[:debugger] ] [ -D[number/list] ] [ -pna ] [ -Fpattern ] [ -l[octal] ] [ -0[octal] ] [ -Idir ] [ -m[-]module ] [ -M[-]'module...' ] [ -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.

Overview

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

Tutorials

    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

    perlstyle		Perl style guide

    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
    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
      perlothrtut	  Old Perl threads tutorial

    perlport		Perl portability guide
    perllocale		Perl locale support
    perluniintro	Perl Unicode introduction
    perlunicode		Perl Unicode support
    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

    perlutil		utilities packaged with the Perl distribution

    perlcompile		Perl compiler suite intro

    perlfilter		Perl source filters

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

    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

Miscellaneous

    perlbook		Perl book information
    perltodo		Perl things to do

    perlhist		Perl history records
    perldelta		Perl changes since previous version
    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

Language-Specific

    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)

Platform-Specific

    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
    perlhpux		Perl notes for HP-UX
    perlhurd		Perl notes for Hurd
    perlirix		Perl notes for Irix
    perlmachten		Perl notes for Power MachTen
    perlmacos		Perl notes for Mac OS (Classic)
    perlmint		Perl notes for MiNT
    perlmpeix		Perl notes for MPE/iX
    perlnetware		Perl notes for NetWare
    perlos2		Perl notes for OS/2
    perlos390		Perl notes for OS/390
    perlplan9		Perl notes for Plan 9
    perlqnx		Perl notes for QNX
    perlsolaris 	Perl notes for Solaris
    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

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:

    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:

• 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.

• compilability into C code or Perl bytecode

  Described in B and B::Bytecode.

• support for light-weight processes (threads)

  Described in perlthrtut and Thread.

• support for internationalization, localization, and Unicode

  Described in perllocale and utf8.

• 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 perlport/"Supported Platforms" 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 perl- .

 "@INC"			locations of perl libraries

 a2p	awk to perl translator
 s2p	sed to perl translator

 http://www.perl.com/       the Perl Home Page
 http://www.cpan.org/       the Comprehensive Perl Archive
 http://www.perl.org/       Perl Mongers (Perl user groups)

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.