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PERL(1) Perl Programmers Reference Guide PERL(1)

NAME

perl – The Perl 5 language interpreter

SYNOPSIS

perl [ -sTtuUWX ] [ -hv ] [ -V[:configvar] ] [ -cw ] [ -d[t][:debugger] ] [ -D[number/list] ] [ -pna ] [ -Fpattern ] [ -l[octal] ] [ -0[octal/hexadecimal] ] [ -Idir ] [ -m[-]module ] [ -M[-]’module…’ ] [ -f ] [ -C [number/list] ] [ -S ] [ -x[dir] ] [ -i[extension] ] [ [-e|-E] ‘command’ ] [ — ] [ programfile ] [ argument ]…

For more information on these options, you can run “perldoc perlrun”.

GETTING HELP
The perldoc program gives you access to all the documentation that
comes with Perl. You can get more documentation, tutorials and
community support online at .

If you’re new to Perl, you should start by running “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
“perldoc perldoc” to learn more things you can do with perldoc.

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
perlrun Perl execution and options
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

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

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
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
perlunicook Perl Unicode cookbook
perlunifaq Perl Unicode FAQ
perluniprops Index of Unicode 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

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

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
perl5221delta Perl changes in version 5.22.1
perl5220delta Perl changes in version 5.22.0
perl5203delta Perl changes in version 5.20.3
perl5202delta Perl changes in version 5.20.2
perl5201delta Perl changes in version 5.20.1
perl5200delta Perl changes in version 5.20.0
perl5184delta Perl changes in version 5.18.4
perl5182delta Perl changes in version 5.18.2
perl5181delta Perl changes in version 5.18.1
perl5180delta Perl changes in version 5.18.0
perl5163delta Perl changes in version 5.16.3
perl5162delta Perl changes in version 5.16.2
perl5161delta Perl changes in version 5.16.1
perl5160delta Perl changes in version 5.16.0
perl5144delta Perl changes in version 5.14.4
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
perl5125delta Perl changes in version 5.12.5
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

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
perlandroid Perl notes for Android
perlbs2000 Perl notes for POSIX-BC BS2000
perlce Perl notes for WinCE
perlcygwin Perl notes for Cygwin
perldos Perl notes for DOS
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
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
perlsynology Perl notes for Synology
perltru64 Perl notes for Tru64
perlvms Perl notes for VMS
perlvos Perl notes for Stratus VOS
perlwin32 Perl notes for Windows

Stubs for Deleted Documents
perlboot
perlbot
perlrepository
perltodo
perltooc
perltoot

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
program or perldoc.

Some documentation is not available as man pages, so if a cross-
reference is not found by man, try it with perldoc. Perldoc can also
take you directly to documentation for functions (with the -f switch).
See “perldoc –help” (or “perldoc perldoc” or “man perldoc”) for other
helpful options perldoc has to offer.

In general, if something strange has gone wrong with your program and
you’re not sure where you should look for help, try making your code
comply with use strict and use warnings. These will often point out
exactly where the trouble is.

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). It combines
(in the author’s opinion, anyway) some of the best features of sed,
awk, and sh, making it familiar and easy to use for Unix users to whip
up quick solutions to annoying problems. Its general-purpose
programming facilities support procedural, functional, and object-
oriented programming paradigms, making Perl a comfortable language for
the long haul on major projects, whatever your bent.

Perl’s roots in text processing haven’t been forgotten over the years.
It still boasts some of the most powerful regular expressions to be
found anywhere, and its support for Unicode text is world-class. It
handles all kinds of structured text, too, through an extensive
collection of extensions. Those libraries, collected in the CPAN,
provide ready-made solutions to an astounding array of problems. When
they haven’t set the standard themselves, they steal from the best —
just like Perl itself.

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 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 .

FILES
“@INC” locations of perl libraries

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

DIAGNOSTICS
Using the “use strict” pragma ensures that all variables are properly
declared and prevents other misuses of legacy Perl features.

The “use warnings” pragma produces some lovely diagnostics. One can
also use the -w flag, but its use is normally discouraged, because it
gets applied to all executed Perl code, including that not under your
control.

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 use
warnings pragma?

BUGS

The behavior implied by the use warnings pragma 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 perlbug@perl.org . 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 v5.22.1 2016-03-13 PERL(1)