Freely Available Perl Resource - Modern Perl by Chromatic
Modern Perl by Chromatic is a freely available Perl eBook. It is a good resource for folks already familiar with programming that want to get up to speed quickly on Perl conventions and syntax.
Previously I used to use a collection of OReilly books to cover this territory but have replaced with 1 copy of Modern Perl (well with the exception of the Cookbooks, you will pry them out of my cold dead hands).
The PDF eBook is freely available via the website above, the hardcopy version is about $35 from major book retailers.