For ease of access, the Perl manual has been split up into a number of sections:
perl Perl overview (this section)
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
perlvar Perl predefined variables
perlsub Perl subroutines
perlmod Perl modules
perlref Perl references
perldsc Perl data structures intro
perllol Perl data structures: lists of lists
perlobj Perl objects
perltie Perl objects hidden behind simple variables
perlbot Perl OO tricks and examples
perldebug Perl debugging
perldiag Perl diagnostic messages
perlform Perl formats
perlipc Perl interprocess communication
perlsec Perl security
perltrap Perl traps for the unwary
perlstyle Perl style guide
perlxs Perl XS application programming interface
perlxstut Perl XS tutorial
perlguts Perl internal functions for those doing extensions
perlcall Perl calling conventions from C
perlembed Perl how to embed perl in your C or C++ app
perlpod Perl plain old documentation
perlbook Perl book information
(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.)
Additional documentation for Perl modules is available in the /usr/local/man/ directory. Some of this is distributed standard with Perl, but you'll also find third-party modules there. You should be able to view this with your man(1) program by including the proper directories in the appropriate start-up files. To find out where these are, type:
perl -le 'use Config; print "@Config{man1dir,man3dir}"'
If the directories were /usr/local/man/man1 and /usr/local/man/man3,
you would only need to add /usr/local/man to your MANPATH. If
they are different, 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 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 quite 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 hash tables used by associative arrays grow as necessary to prevent degraded performance. Perl uses sophisticated pattern matching techniques to scan large amounts of data very quickly. Although optimized for scanning text, Perl can also deal with binary data, and can make dbm files look like associative arrays. Setuid Perl scripts are safer than C programs through a dataflow tracing mechanism which 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...
Perl version 5 is nearly a complete rewrite, and provides
the following additional benefits:
Ok, that's definitely enough hype.
use lib "/my/directory";
BEGIN { require 'perl5db.pl' }
Apart from these, Perl uses no other environment variables, except to make them available to the script being executed, and to child processes. However, scripts running setuid would do well to execute the following lines before doing anything else, just to keep people honest:
$ENV{'PATH'} = '/bin:/usr/bin'; # or whatever you need
$ENV{'SHELL'} = '/bin/sh' if defined $ENV{'SHELL'};
$ENV{'IFS'} = '' if defined $ENV{'IFS'};
"/tmp/perl-e$$" temporary file for -e commands "@INC" locations of perl 5 libraries
a2p awk to perl translator
s2p sed to perl translator
See the perldiag manpage for explanations of all Perl's diagnostics.
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 the case of 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?
Perl is at the mercy of your machine's definitions of various operations such as type casting, atof() and sprintf(). The latter can even trigger a coredump when passed ludicrous input values.
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 identifier may not be longer than 255 characters, and no component of your PATH may be longer than 255 if you use -S. A regular expression may not compile to more than 32767 bytes internally.
See the perl bugs database at http://perl.com/perl/bugs/ . You may mail your bug reports (be sure to include full configuration information as output by the myconfig program in the perl source tree) to perlbug@perl.com. 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 three principal virtues of a programmer are Laziness, Impatience, and Hubris. See the Camel Book for why.