I think the previous posts give a good run down on the O'Rielly books, but there are 2 books not mentioned that you may want to consider.

Even though you may not be interested in Object Oriented perl, I didn't realize how much 'essential perl' I was lacking until I went through Damien Conways Object Oriented perl. (Published by Manning IBSN 1-884777-79-1). If you can't afford to add it to your collection I still think snagging the book at a Barnes and Nobles and reading the second chapter would be very enlightenning for a beginner. Not that I'd ever do such a thing :)

The other book that I'm finding is becomming the most dog eared and quickest reference book is Perl Core Language (Little Black Book Series) from Corolis Press. (ISBN 1-57610-426-5). There's nothing in it that's not covered by the O'Rielly books but it's better organized for those 'quick refreshers' IMHO.