=head1 NAME

perl - Practical Extraction and Report Language

=head1 SYNOPSIS

B<perl> S<[ B<-sTuU> ]> S<[ B<-hv> ] [ B<-V>[:I<configvar>] ]>

S<[ B<-cw> ] [ B<-d>[:I<debugger>] ] [ B<-D>[I<number/list>] ]>

S<[ B<-pna> ] [ B<-F>I<pattern> ] [ B<-l>[I<octal>] ] [ B<-0>[I<octal>] ]>

S<[ B<-I>I<dir> ] [ B<-m>[B<->]I<module> ] [ B<-M>[B<->]I<'module...'> ]>

S<[ B<-P> ]> S<[ B<-S> ]> S<[ B<-x>[I<dir>] ]>

S<[ B<-i>[I<extension>] ]> S<[ B<-e> I<'command'> ]

[ B<--> ] [ I<programfile> ] [ I<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

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.)

By default, the manpages listed above are installed in the

F</usr/local/man/> directory.

Extensive additional documentation for Perl modules is available. The

default configuration for perl will place this additional documentation

in the F</usr/local/lib/perl5/man> directory (or else in the F<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 F</usr/local/man/man1>

and F</usr/local/man/man3>, you need only to add that stem

(F</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 F<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 B<-w> switch first. It

will often point out exactly where the trouble is.

=head1 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, B<sed>, B<awk>, and B<sh>, so people familiar with

those languages should have little difficulty with it. (Language

historians will also note some vestiges of B<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 B<sed> or B<awk> or

B<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 B<sed> and B<awk>

scripts into Perl scripts.

But wait, there's more...

Begun in 1993 (see L<perlhist>), Perl version 5 is nearly a complete

rewrite that provides the following additional benefits:

=over 4

=item *

modularity and reusability using innumerable modules

Described in L<perlmod>, L<perlmodlib>, and L<perlmodinstall>.

=item *

embeddable and extensible

Described in L<perlembed>, L<perlxstut>, L<perlxs>, L<perlcall>,

L<perlguts>, and L<xsubpp>.

=item *

roll-your-own magic variables (including multiple simultaneous DBM implementations)

Described in L<perltie> and L<AnyDBM_File>.

=item *

subroutines can now be overridden, autoloaded, and prototyped

Described in L<perlsub>.

=item *

arbitrarily nested data structures and anonymous functions

Described in L<perlreftut>, L<perlref>, L<perldsc>, and L<perllol>.

=item *

object-oriented programming

Described in L<perlobj>, L<perltoot>, and L<perlbot>.

=item *

compilability into C code or Perl bytecode

Described in L<B> and L<B::Bytecode>.

=item *

support for light-weight processes (threads)

Described in L<perlthrtut> and L<Thread>.

=item *

support for internationalization, localization, and Unicode

Described in L<perllocale> and L<utf8>.

=item *

lexical scoping

Described in L<perlsub>.

=item *

regular expression enhancements

Described in L<perlre>, with additional examples in L<perlop>.

=item *

enhanced debugger and interactive Perl environment,

with integrated editor support

Described in L<perldebug>.

=item *

POSIX 1003.1 compliant library

Described in L<POSIX>.

=back

Okay, that's I<definitely> enough hype.

=head1 AVAILABILITY

Perl is available for most operating systems, including virtually

all Unix-like platforms. See L<perlport/"Supported Platforms">

for a listing.

=head1 ENVIRONMENT

See L<perlrun>.

=head1 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 .

=head1 FILES

"@INC" locations of perl libraries

=head1 SEE ALSO

a2p awk to perl translator

s2p sed to perl translator

http://www.perl.com/ the Perl Home Page

http://www.perl.com/CPAN the Comprehensive Perl Archive

=head1 DIAGNOSTICS

The C<use warnings> pragma (and the B<-w> switch) produces some

lovely diagnostics.

See L<perldiag> for explanations of all Perl's diagnostics. The C<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 B<-e> switches, each

B<-e> is counted as one line.)

Setuid scripts have additional constraints that can produce error

messages such as "Insecure dependency". See L<perlsec>.

Did we mention that you should definitely consider using the B<-w>

switch?

=head1 BUGS

The B<-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 C<perl -V>) to perlbug@perl.org . If you've succeeded

in compiling perl, the B<perlbug> script in the F<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.

=head1 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.