As a beginner or journeyman Perl programmer I've been able to do useful work in the language without ever using anything more advanced than an occaisional reference. What are (I guess) the most elementary parts of the language enable me to do many things that are too slow, too clumsy, or just outright impossible in any Unix shell.
I am finding that the book:
"Learning Perl Objects, References, & Modules"
by Randal L. Schwartz with Tom Phoenix
is immensely helpful to me in learning about the more advanced features of Perl. It introduces concepts in a natural (probably not the only possible) order, it almost completely avoids the maddening practice of using a term before defining it, it provides good examples and exercises that really help me absorb the lessons (especially if I actually do the exercises and type up, run, & play with the examples in the text), and it introduces some core modules and illustrates why you might want to use them.
No, I'm not trying to sell the book, there may be other ones just as good or better, and maybe there are better choices of 'first modules' to introduce to the journeyman Perl coder. But I have to say that so far (I'm about half through it), this is IMHO a very good '2.0' or even '3.0' level tutorial for someone trying to learn beyond the very basics of the language.