Perl isn't just a programming language, it's a culture, and this book—more than any other—is your guide, introduction and reference to the culture that is Perl.

Beginning Perl is great, but it omits references, which are crucial to understanding arbitrary complex perl data structures.

After a short introduction (called "Introduction"), Part I, "Introduction to Perl Debugging", contains a single chapter called (rather confusingly) "Introduction".

Almost all classes have used Java to teach OO concepts. One of my last classes is an intro to Perl. The (very little) research I've done indicates that Perl isn't commonly used nowadays.