Perl is in a state of (comparatively) rapid change, and has gotten into the position where the best documentation beyond a basic introduction to Perl 5 -- the current major version -- is the electronic documentation which comes with the language itself.
Read 'perldoc perlintro', then look to 'perldoc perl' for the rest of the core language documentation. Note that on Debian systems, you'll need to 'apt-get install perl-doc' to get this documentation.
Once you've got a handle on things, check out 'perldoc perldelta' to see what's new in the version of Perl installed on your system (which should be 5.8.8 or 5.10 these days -- much cool stuff in 5.10!). If the perldelta page isn't making any sense (and believe me, I remember how that feels), just come back to it later.
Finally, freenode #perl for questions you can't find answers to in the docs.
