I would also recommend a hard smack in the head with some OO language like Java (and I don't even think Java is all that OO; it's just OO enough to be disruptive)

And a kick in the face with something functional like LISP/Scheme.

What I mean with the above two lines is: nobody can be a good programmer without *really understanding* OO and functional programming.

the great thing about perl is, that you can actually use *most* functional and OO techniques without being forced to.

update: more than any book I know, the camel book will teach you "the perl way" - i.e it will explain how to do stuff and why. I can recommend many more books, but if you're going for perl, it's at the top of the list for me.