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Practical Extraction and Report Language

perl - Practical Extraction and Report Language


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 ]...

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

    perl                Perl overview (this section)

    perldelta           Perl changes since previous version

    perl5005delta       Perl changes in version 5.005

    perl5004delta       Perl changes in version 5.004

    perlfaq             Perl frequently asked questions

    perltoc             Perl documentation table of contents

    perldata            Perl data structures

    perlsyn             Perl syntax

    perlop              Perl operators and precedence

    perlre              Perl regular expressions

    perlrun             Perl execution and options

    perlfunc            Perl builtin functions

    perlopentut         Perl open() tutorial

    perlvar             Perl predefined variables

    perlsub             Perl subroutines

    perlmod             Perl modules: how they work

    perlmodlib          Perl modules: how to write and use

    perlmodinstall      Perl modules: how to install from CPAN

    perlform            Perl formats

    perlunicode         Perl unicode support

    perllocale          Perl locale support

    perlreftut          Perl references short introduction

    perlref             Perl references, the rest of the story

    perldsc             Perl data structures intro

    perllol             Perl data structures: arrays of arrays

    perlboot            Perl OO tutorial for beginners

    perltoot            Perl OO tutorial, part 1

    perltootc           Perl OO tutorial, part 2

    perlobj             Perl objects

    perltie             Perl objects hidden behind simple variables

    perlbot             Perl OO tricks and examples

    perlipc             Perl interprocess communication

    perlfork            Perl fork() information

    perlthrtut          Perl threads tutorial

    perllexwarn         Perl warnings and their control

    perlfilter          Perl source filters

    perldbmfilter       Perl DBM filters

    perlcompile         Perl compiler suite intro

    perldebug           Perl debugging

    perldiag            Perl diagnostic messages

    perlnumber          Perl number semantics

    perlsec             Perl security

    perltrap            Perl traps for the unwary

    perlport            Perl portability guide

    perlstyle           Perl style guide

    perlpod             Perl plain old documentation

    perlbook            Perl book information

    perlembed           Perl ways to embed perl in your C or C++ application

    perlapio            Perl internal IO abstraction interface

    perldebguts         Perl debugging guts and tips

    perlxs              Perl XS application programming interface

    perlxstut           Perl XS tutorial

    perlguts            Perl internal functions for those doing extensions

    perlcall            Perl calling conventions from C

    perlapi             Perl API listing (autogenerated)

    perlintern          Perl internal functions (autogenerated)

    perltodo            Perl things to do

    perlhack            Perl hackers guide

    perlhist            Perl history records

    perlamiga           Perl notes for Amiga

    perlcygwin          Perl notes for Cygwin

    perldos             Perl notes for DOS

    perlhpux            Perl notes for HP-UX

    perlmachten         Perl notes for Power MachTen

    perlos2             Perl notes for OS/2

    perlos390           Perl notes for OS/390

    perlvms             Perl notes for VMS

    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.)

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:

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 .


 "@INC"                 locations of perl libraries


 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.