perl - Practical Extraction and Report Language


perl [ __-sTuU__? [ __-hv__? ''configvar''? ] [ __-cw__? ''debugger''? ] __-D__[[''number/list''? ] [ __-pna__? __-F__''pattern''? [ __-l__[[''octal''? ] __-0__[[''octal''? ] [ __-I__''dir''? __-m__[[__-__?module ] __-M__[[__-__?'module...' ] [ __-P__? __-S__? [ __-x__[[''dir''? ] __-i__[[''extension''? ] [ __-e__ '''command'''? [ __--__? [ ''programfile''? [ ''argument''?...

For ease of access, the Perl manual has been split up into

several sections
perl Perl overview (this section)

perlfaq Perl frequently asked questions perltoc Perl documentation table of contents perlbook Perl book information

perlsyn Perl syntax

perldata Perl data structures perlop Perl operators and precedence perlsub Perl subroutines perlfunc Perl builtin functions perlreftut Perl references short introduction perldsc Perl data structures intro perlrequick Perl regular expressions quick start perlpod Perl plain old documentation perlstyle Perl style guide perltrap Perl traps for the unwary

perlrun Perl execution and options

perldiag Perl diagnostic messages perllexwarn Perl warnings and their control perldebtut Perl debugging tutorial perldebug Perl debugging

perlvar Perl predefined variables

perllol Perl data structures: arrays of arrays perlopentut Perl open() tutorial perlretut Perl regular expressions tutorial

perlre Perl regular expressions, the rest of the story

perlref Perl references, the rest of the story

perlform Perl formats perlboot Perl OO tutorial for beginners

perltoot Perl OO tutorial, part 1 perltootc Perl OO tutorial, part 2 perlobj Perl objects perlbot Perl OO tricks and examples perltie Perl objects hidden behind simple variables

perlipc Perl interprocess communication

perlfork Perl fork() information perlnumber Perl number semantics perlthrtut Perl threads tutorial

perlport Perl portability guide

perllocale Perl locale support 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 perlmodinstall Perl modules: how to install from CPAN perlnewmod Perl modules: preparing a new module for distribution

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

perlcompile Perl compiler suite intro 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 perlutil utilities packaged with the Perl distribution perlfilter Perl source filters (package: libfilter-perl) perldbmfilter Perl DBM filters perlapi Perl API listing (autogenerated) perlintern Perl internal functions (autogenerated) perlapio Perl internal IO abstraction interface perltodo Perl things to do perlhack Perl hackers guide

perlhist Perl history records

perldelta Perl changes since previous version perl5005delta Perl changes in version 5.005 perl5004delta Perl changes in version 5.004

perlaix Perl notes for AIX

perlamiga Perl notes for Amiga perlbs2000 Perl notes for POSIX-BC BS2000 perlcygwin Perl notes for Cygwin perldos Perl notes for DOS perlepoc Perl notes for EPOC perlhpux Perl notes for HP-UX perlmachten Perl notes for Power !MachTen? perlmacos Perl notes for Mac OS (Classic) perlmpeix Perl notes for MPE/iX perlos2 Perl notes for OS/2 perlos390 Perl notes for OS/390 perlsolaris Perl notes for Solaris perlvmesa Perl notes for VM/ESA perlvms Perl notes for VMS perlvos Perl notes for Stratus VOS perlwin32 Perl notes for Windows (If you're intending to read these straight through for the first time, the suggested order will tend to reduce the number of forward references.)

On Debian systems, you need to install the perl-doc package which contains the majority of the standard Perl documentation and the perldoc program.

Extensive additional documentation for Perl modules is available, both those distributed with Perl and third-party modules which are packaged or locally installed.

You should be able to view Perl's documentation with your man(1) program or perldoc(1).

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, perltoot, 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 perldebug.

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

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 .



a2p awk to perl translator

s2p sed to perl translator the Perl Home Page the Comprehensive Perl Archive


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.

Knowing your camels: the dromedary has one hump; the Bactrian camel two; a perl is any camel with three or more humps, or more than five legs.

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