PERL(1) Perl Programmers Reference Guide PERL(1)
NAME
perl - Practical Extraction and Report Language
SYNOPSIS
perl [ -sTtuUWX ] [ -hv ] [ -V[:configvar] ] [ -cw ] [ -d[t][:debug-
ger] ] [ -D[number/list] ] [ -pna ] [ -Fpattern ] [ -l[octal] ] [ -0[octal/hexadeci-
mal] ] [ -Idir ] [ -m[-]module ] [ -M[-]'module...' ] [ -f ] [ -C [num-
ber/list] ] [ -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
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
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
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
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
perlglossary Perl Glossary
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
perldoc Look up Perl documentation in Pod format
perlhist Perl history records
perldelta Perl changes since previous version
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
perl573delta Perl changes in version 5.7.3
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
perlartistic Perl Artistic License
perlgpl GNU General Public License
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
perllinux Perl notes for Linux
perlmachten Perl notes for Power MachTen
perlmacos Perl notes for Mac OS (Classic)
perlmacosx Perl notes for Mac OS X
perlmint Perl notes for MiNT
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
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 configura-
tion 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 documen-
tation 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 vari-
able. 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) con-
figuration 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:
? 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, perlboot, perltoot, perltooc, and perlbot.
? support for light-weight processes (threads)
Described in perlthrtut and threads.
? support for Unicode, internationalization, and localization
Described in perluniintro, perllocale and Locale::Maketext.
? 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 perldebtut, perldebug and perldebguts.
? POSIX 1003.1 compliant library
Described in POSIX.
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 <>, with the help of oodles of other folks.
If your Perl success stories and testimonials may be of help to others who wish to advo-
cate the use of Perl in their applications, or if you wish to simply express your grati-
tude to Larry and the Perl developers, please write to .
FILES
"@INC" locations of perl libraries
SEE ALSO
a2p awk to perl translator
s2p sed to perl translator
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
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 "Inse-
cure 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 .
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.
perl v5.8.8 2006-01-07 PERL(1)
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