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perl-5.8.0
River stage five • 11759 direct dependents • 33295 total dependents
/ pod/perl.pod

NAME

perl - Practical Extraction and Report Language

SYNOPSIS

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.

DESCRIPTION

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.

AVAILABILITY

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

ENVIRONMENT

See perlrun.

AUTHOR

Larry Wall <larry@wall.org>, 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-thanks@perl.org .

FILES

"@INC"			locations of perl libraries

SEE ALSO

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)

DIAGNOSTICS

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?

BUGS

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 perlbug@perl.org . 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.

NOTES

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.