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# perl

- NAME
- SYNOPSIS
- DESCRIPTION
- AVAILABILITY
- ENVIRONMENT
- AUTHOR
- FILES
- SEE ALSO
- DIAGNOSTICS
- BUGS
- NOTES

## NAME

perl - Practical Extraction and Report Language

## SYNOPSIS

perl [ -sTuU ] [ -hv ] [ -V[:configvar] ]
[ -cw ] [ -d[:debugger] ] [ -D[number/list] ]
[ -pna ] [ -Fpattern ] [ -l[octal] ] [ -0[octal] ]
[ -Idir ] [ -m[-]module ] [ -M[-]'module...' ]
[ -P ] [ -S ] [ -x[dir] ]
[ -i[extension] ] [ -e 'command' ]
[ -- ] [ programfile ] [ 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
        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 `/usr/local/man/` directory.

Extensive additional documentation for Perl modules is available. The default configuration 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 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 `/usr/local/man/man1` and `/usr/local/man/man3`, you need only to add that stem (`/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 `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 the perlhist manpage), Perl version 5 is nearly a complete rewrite that provides the following additional benefits:

- modularity and reusability using innumerable modules

  Described in the perlmod manpage, the perlmodlib manpage, and the perlmodinstall manpage.

- embeddable and extensible

  Described in the perlembed manpage, the perlxstut manpage, the perlxs manpage, the perlcall manpage, the perlguts manpage, and the xsubpp manpage.

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

  Described in the perltie manpage and the AnyDBM_File manpage.

- subroutines can now be overridden, autoloaded, and prototyped

  Described in the perlsub manpage.

- arbitrarily nested data structures and anonymous functions

  Described in the perlreftut manpage, the perlref manpage, the perldsc manpage, and the perllol manpage.

- object-oriented programming

  Described in the perlobj manpage, the perltoot manpage, and the perlbot manpage.

- compilability into C code or Perl bytecode

  Described in the B manpage and the B::Bytecode manpage.

- support for light-weight processes (threads)

  Described in the perlthrtut manpage and the Thread manpage.

- support for internationalization, localization, and Unicode

  Described in the perllocale manpage and the utf8 manpage.

- lexical scoping

  Described in the perlsub manpage.

- regular expression enhancements

  Described in the perlre manpage, with additional examples in the perlop manpage.

- enhanced debugger and interactive Perl environment, with integrated editor support

  Described in the perldebug manpage.

- POSIX 1003.1 compliant library

  Described in the POSIX manpage.

Okay, that's definitely enough hype.

## AVAILABILITY

Perl is available for most operating systems, including virtually all Unix-like platforms. See the section on Supported Platforms in the perlport manpage for a listing.

## ENVIRONMENT

See the perlrun manpage.

## 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 .

## FILES

     "@INC"			locations of perl libraries

## 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

## DIAGNOSTICS

The `use warnings` pragma (and the -w switch) produces some lovely diagnostics.

See the perldiag manpage 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 the perlsec manpage.

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 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.

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