perl.pod in perl-5.20.1
perl - The Perl 5 language interpreter
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
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 http://www.perl.org/.
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.
perl Perl overview (this section) perlintro Perl introduction for beginners perlrun Perl execution and options perltoc Perl documentation table of contents
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
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 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
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 perl5200delta Perl changes in version 5.20.0 perl5182delta Perl changes in version 5.18.2 perl5181delta Perl changes in version 5.18.1 perl5180delta Perl changes in version 5.18.0 perl5161delta Perl changes in version 5.16.1 perl5162delta Perl changes in version 5.16.2 perl5163delta Perl changes in version 5.16.3 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
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)
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 a Unix-like system, these documentation files will usually also be available as manpages for use with the man program.
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.
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.
Perl is available for most operating systems, including virtually all Unix-like platforms. See "Supported Platforms" in perlport for a listing.
Larry Wall <firstname.lastname@example.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 email@example.com .
"@INC" locations of perl libraries
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
use strict pragma ensures that all variables are properly declared and prevents other misuses of legacy Perl features.
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?
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 firstname.lastname@example.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.
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.