Perl is one of the most popular programming languages and it comes pre-installed with any copy of Mac OS X. It lives in /usr/bin/perl on your computer.
Perl is a general purpose language and is used to perform a wide range of tasks (although there is a common misconception that it is just a ScriptingLanguage for quick and dirty operations). Its traditional strengths lie in text processing (Perl has an integrated powerful pattern-matching engine), UNIX shell scripting and CGI (dynamic web pages), but you can develop GUI applications as well.
There is a strong developers’ community behind Perl and they are usually very eager to help out with questions about it. A good starting point is the Perl directory at http://www.perl.org/
A good place to lurk (and eventually ask questions) while you’re learning Perl is http://www.perlmonks.org/
Unlike some forums, the members run the gamut of expertise from absolute beginners to people actually working on the next implementation of the language.
This WikiWikiWeb is implemented in perl. A single perl script does it all, in fact.
Perl is famous for the fact that “there is more than one way to do it” (TIMTOWTDI), the same Perl script can be written in a hundred different ways, more or less readable, but usually less.
This is how one would read all the lines of a file and output them on STDOUT (could be made shorter, maybe a JAPH [Just Another Perl Hacker] could try?):
perl -e ‘print <>’ filename
Okay, here’s a shorter one:
perl -pe * filename
Perhaps the best feature of Perl is how integrated pattern matching is to the whole language; with Perl 6, it will supposedly get a whole lot more so, but that’s a little while off yet.
Another good thing about it is that Perl is very cross-platform (most Perl programs work on Mac, UNIX and Windows).
CamelBones is an ObjC bridge for Perl. It allows you to write Cocoa apps in Perl or use Perl from Objective-C.
You could also have a look at PerlObjCBridge.
Mac::Glue [http://search.cpan.org/~cnandor/Mac-Glue/] allows Perl to communicate with AppleScriptable applications.
PerlPad is a Cocoa app (based on CamelBones) that lets you execute Perl statements as a System Service.