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=head1 NAME
perl - The Perl 5 language interpreter
=head1 SYNOPSIS
B<perl> S<[ B<-sTtuUWX> ]>
S<[ B<-hv> ] [ B<-V>[:I<configvar>] ]>
S<[ B<-cw> ] [ B<-d>[B<t>][:I<debugger>] ] [ B<-D>[I<number/list>] ]>
S<[ B<-pna> ] [ B<-F>I<pattern> ] [ B<-l>[I<octal>] ] [ B<-0>[I<octal/hexadecimal>] ]>
S<[ B<-I>I<dir> ] [ B<-m>[B<->]I<module> ] [ B<-M>[B<->]I<'module...'> ] [ B<-f> ]>
S<[ B<-C [I<number/list>] >]>
S<[ B<-S> ]>
S<[ B<-x>[I<dir>] ]>
S<[ B<-i>[I<extension>] ]>
S<[ [B<-e>|B<-E>] I<'command'> ] [ B<--> ] [ I<programfile> ] [ I<argument> ]...>
=head1 GETTING HELP
The F<perldoc> program gives you access to all the documentation that comes
with Perl. You can get more documentation, tutorials and community support
online at L<http://www.perl.org/>.
If you're new to Perl, you should start by running C<perldoc perlintro>,
which is a general intro for beginners and provides some background to help
you navigate the rest of Perl's extensive documentation. Run C<perldoc
perldoc> to learn more things you can do with F<perldoc>.
For ease of access, the Perl manual has been split up into several sections.
=begin buildtoc
# This section is parsed by Porting/pod_lib.pl for use by pod/buildtoc etc
flag =g perluniprops perlmodlib perlapi perlintern
flag =go perltoc
flag =ro perlcn perljp perlko perltw
flag = perlvms
path perlfaq.* cpan/perlfaq/lib/
path perlglossary cpan/perlfaq/lib/
path perlxs(?:tut|typemap)? dist/ExtUtils-ParseXS/lib/
path perldoc cpan/Pod-Perldoc/lib/
aux a2p c2ph h2ph h2xs perlbug pl2pm pod2html pod2man s2p splain xsubpp
=end buildtoc
=head2 Overview
perl Perl overview (this section)
perlintro Perl introduction for beginners
perltoc Perl documentation table of contents
=head2 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
perlootut Perl OO tutorial for beginners
perlperf Perl Performance and Optimization Techniques
perlstyle Perl style guide
perlcheat Perl cheat sheet
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
=head2 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
perlpodstyle Perl POD style guide
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
perlrebackslash Perl regular expression backslash sequences
perlrecharclass Perl regular expression character classes
perlreref Perl regular expressions quick reference
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
perlport Perl portability guide
perllocale Perl locale support
perluniintro Perl Unicode introduction
perlunicode Perl Unicode support
perlunifaq Perl Unicode FAQ
perluniprops Index of Unicode Version 6.0.0 properties in Perl
perlunitut Perl Unicode tutorial
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
perlpragma Perl modules: writing a user pragma
perlutil utilities packaged with the Perl distribution
perlfilter Perl source filters
perldtrace Perl's support for DTrace
perlglossary Perl Glossary
=head2 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
perlxstypemap Perl XS C/Perl type conversion tools
perlclib Internal replacements for standard C library functions
perlguts Perl internal functions for those doing extensions
perlcall Perl calling conventions from C
perlmroapi Perl method resolution plugin interface
perlreapi Perl regular expression plugin interface
perlreguts Perl regular expression engine internals
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
perlsource Guide to the Perl source tree
perlinterp Overview of the Perl interpreter source and how it works
perlhacktut Walk through the creation of a simple C code patch
perlhacktips Tips for Perl core C code hacking
perlpolicy Perl development policies
perlgit Using git with the Perl repository
=head2 Miscellaneous
perlbook Perl book information
perlcommunity Perl community information
perldoc Look up Perl documentation in Pod format
perlhist Perl history records
perldelta Perl changes since previous version
perl5162delta Perl changes in version 5.16.2
perl5161delta Perl changes in version 5.16.1
perl5160delta Perl changes in version 5.16.0
perl5160delta Perl changes in version 5.16.0
perl5143delta Perl changes in version 5.14.3
perl5142delta Perl changes in version 5.14.2
perl5141delta Perl changes in version 5.14.1
perl5140delta Perl changes in version 5.14.0
perl5124delta Perl changes in version 5.12.4
perl5123delta Perl changes in version 5.12.3
perl5122delta Perl changes in version 5.12.2
perl5121delta Perl changes in version 5.12.1
perl5120delta Perl changes in version 5.12.0
perl5101delta Perl changes in version 5.10.1
perl5100delta Perl changes in version 5.10.0
perl589delta Perl changes in version 5.8.9
perl588delta Perl changes in version 5.8.8
perl587delta Perl changes in version 5.8.7
perl586delta Perl changes in version 5.8.6
perl585delta Perl changes in version 5.8.5
perl584delta Perl changes in version 5.8.4
perl583delta Perl changes in version 5.8.3
perl582delta Perl changes in version 5.8.2
perl581delta Perl changes in version 5.8.1
perl58delta Perl changes in version 5.8.0
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
perlexperiment A listing of experimental features in Perl
perlartistic Perl Artistic License
perlgpl GNU General Public License
=head2 Language-Specific
=for buildtoc flag +r
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)
=head2 Platform-Specific
perlaix Perl notes for AIX
perlamiga Perl notes for AmigaOS
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
perlhaiku Perl notes for Haiku
perlhpux Perl notes for HP-UX
perlhurd Perl notes for Hurd
perlirix Perl notes for Irix
perllinux Perl notes for Linux
perlmacos Perl notes for Mac OS (Classic)
perlmacosx Perl notes for Mac OS X
perlmpeix Perl notes for MPE/iX
perlnetware Perl notes for NetWare
perlopenbsd Perl notes for OpenBSD
perlos2 Perl notes for OS/2
perlos390 Perl notes for OS/390
perlos400 Perl notes for OS/400
perlplan9 Perl notes for Plan 9
perlqnx Perl notes for QNX
perlriscos Perl notes for RISC OS
perlsolaris Perl notes for Solaris
perlsymbian Perl notes for Symbian
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
=for buildtoc flag -r
=head2 Stubs for Deleted Documents
perlboot
perlbot
perltodo
perltooc
perltoot
=for buildtoc __END__
On a Unix-like system, these documentation files will usually also be
available as manpages for use with the F<man> program.
In general, 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 officially stands for Practical Extraction and Report Language,
except when it doesn't.
Perl was originally a language optimized for scanning arbitrary
text files, extracting information from those text files, and printing
reports based on that information. It quickly became a good language
for many system management tasks. Over the years, Perl has grown into
a general-purpose programming language. It's widely used for everything
from quick "one-liners" to full-scale application development.
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 also has many excellent tools for slicing
and dicing binary data.
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<perlxstypemap>,
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> and L<perlootut>.
=item *
support for light-weight processes (threads)
Described in L<perlthrtut> and L<threads>.
=item *
support for Unicode, internationalization, and localization
Described in L<perluniintro>, L<perllocale> and L<Locale::Maketext>.
=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<perldebtut>, L<perldebug> and L<perldebguts>.
=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
http://www.perl.org/ the Perl homepage
http://www.perl.com/ Perl articles (O'Reilly)
http://www.cpan.org/ the Comprehensive Perl Archive
http://www.pm.org/ the Perl Mongers
=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 L<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.