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perl - Practical Extraction and Report Language


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)
perldelta		Perl changes since previous version
perl5005delta	Perl changes in version 5.005
perl5004delta	Perl changes in version 5.004
perlfaq		Perl frequently asked questions
perltoc		Perl documentation table of contents

perldata		Perl data structures
perlsyn		Perl syntax
perlop		Perl operators and precedence
perlre		Perl regular expressions
perlrun		Perl execution and options
perlfunc		Perl builtin functions
perlopentut		Perl open() tutorial
perlvar		Perl predefined variables
perlsub		Perl subroutines
perlmod		Perl modules: how they work
perlmodlib		Perl modules: how to write and use
perlmodinstall	Perl modules: how to install from CPAN
perlform		Perl formats
perlunicode		Perl unicode support
perllocale		Perl locale support

perlreftut		Perl references short introduction
perlref		Perl references, the rest of the story
perldsc		Perl data structures intro
perllol		Perl data structures: arrays of arrays
perlboot		Perl OO tutorial for beginners
perltoot		Perl OO tutorial, part 1
perltootc		Perl OO tutorial, part 2
perlobj		Perl objects
perltie		Perl objects hidden behind simple variables
perlbot		Perl OO tricks and examples
perlipc		Perl interprocess communication
perlfork		Perl fork() information
perlthrtut		Perl threads tutorial
perllexwarn		Perl warnings and their control
perlfilter		Perl source filters
perldbmfilter	Perl DBM filters

perlcompile		Perl compiler suite intro
perldebug		Perl debugging
perldiag		Perl diagnostic messages
perlnumber		Perl number semantics
perlsec		Perl security
perltrap		Perl traps for the unwary
perlport		Perl portability guide
perlstyle		Perl style guide

perlpod		Perl plain old documentation
perlbook		Perl book information

perlembed		Perl ways to embed perl in your C or C++ application
perlapio		Perl internal IO abstraction interface
perldebguts		Perl debugging guts and tips
perlxs		Perl XS application programming interface
perlxstut		Perl XS tutorial
perlguts		Perl internal functions for those doing extensions
perlcall		Perl calling conventions from C
perlapi		Perl API listing (autogenerated)
perlintern		Perl internal functions (autogenerated)

perltodo		Perl things to do
perlhack		Perl hackers guide
perlhist		Perl history records

perlamiga		Perl notes for Amiga
perlcygwin		Perl notes for Cygwin
perldos		Perl notes for DOS
perlhpux		Perl notes for HP-UX
perlmachten		Perl notes for Power MachTen
perlos2		Perl notes for OS/2
perlos390		Perl notes for OS/390
perlvms		Perl notes for VMS
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.


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:

Okay, that's definitely enough hype.


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


See perlrun.


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 .


"@INC"			locations of perl libraries


a2p	awk to perl translator
s2p	sed to perl translator	    the Perl Home Page   the Comprehensive Perl Archive


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 "Insecure dependency". See perlsec.

Did we mention that you should definitely consider using the -w switch?


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.


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.