If you've mastered The Llama (Learning Perl), make haste to read this one. Even if you only want to do scripting with Perl, you'll eventually find you need data structures slightly more complicated than just flat arrays and hashes, and you need to know about references for that. While Programming Perl does contain a fair chunk of material on just this subject, it was a bit too much for me to digest after The Llama. If Intermediate Perl (aka The Alpaca) had been around for me to read, I would have had a much easier time.
Written in the same style as The Llama, this breeze through most of the rest of Perl, in particular: references, objects, packages and modules. These are the bits that you need to use Perl as a general purpose programming language, not just for scripting. In a similar pragmatic vein, it also covers how to use tools to build your own packages in the CPAN style, and there's a good chunk of material on using Test::More for unit tests. Probably the only thing missing is material on type globs and symbol tables, although hopefully, brian d foy's forthcoming Mastering Perl will fill in these gaps.
The bottom line is this is Llama part 2, and you need to read it if you want to have any hope of understanding anyone else's Perl. But I can't give it five stars. The major problem is that the material is not very well organised. At the chapter level, objects are sandwiched between modules and packages. It would have been far preferable to keep the module and package information together. As a result, the distinction between modules and packages is rather muddied, and the introduction of objects in the middle just makes things worse. Overall, I found the explanations to lack the clarity of the Llama.
A more minor complaint is that, while there are mercifully fewer annoying footnotes, the Gilligan's Island theme (fellow people of Britain, read the Wikipedia article before you start) grates far sooner than the Flintstones flavour of the Llama.
That said, make this your second book on Perl. Then, _still_ don't read The Camel yet. Avail yourself of Perl Best Practices first.