Programming Perl is of course very good. But a lot of the information found in it can be found in the on-line documentation. A book that in my opinion really boosts your proficiency in Perl is the Perl Cookbook. It teaches you idiomatic Perl (which most of the time is also the most efficient Perl) for a lot of day-to-day programming problems. Security isn't a topic in itself, but is touch upon in the topics where it matters. perlsec is good source of information about security.

Arjen