I highly recommend this book. I think it was supposed to be released by APress, but for whatever reasons the book was pulled before release. Fortunately for us though, Crow self-published it on Lulu (and discarded the subtitle "secrets of the cpan masters"). It's an excellent book that draws on the insights of the Design Patterns gang of 4 folks, but shows how the idiomatic and creative use of Perl enables better control flow and program organization than would be possible simply applying the ideas of GoF in strictly OO Perl. Crow uses OO technique where they offer an advantage in elegance or clarity, but applies more direct techniques in cases where the OO methodology would only get in the way. Perl is a lot more flexible and expressive than a language like Java or C++ (though less so than Lisp), and this enables Crow to go beyond the GoF patterns and get into techniques of the variety explored in Dominus's classic Higher Order Perl, but in the context of patterns.