Rather than focusing on learning obscure and possibly non-useful idiosyncracies of Perl, I would suggest you learn how to write better perl programs. Read "Perl Medic" by Peter Scott. It is a great book about how to write perl code that you won't be ashamed of in a couple of years. Books like Conway's OO Perl tend to be interesting but impractical. (Should you really do a bunch of obfuscated things to hide your object properties behind closures? Probably not.) I do like the discussion of references and objects in "Advanced Perl Programming" though, and the algorithms books is pretty solid, so those are both excellent choices.