To ask with the words of brian d foy: Um, well, gees, didn't you learn Perl from your previous edition?
I think buying a new edition of the same book is only good if you can look at what the new edition offers you. Personally, I bought the second edition of Mastering Regular Expressions, because it has lots of ugly details on Unicode and also provides me with a roadmap to the regular expression engines available in those other languages I keep hearing rumors about. But usually, a new edition doesn't provide much new information over the old edition and thus isn't worth the "upgrade".
