I've been a programmer for several years, and when I pick up a book to learn a new language, I don't wan't it to take several pages explaining what a variable is. From the outset, Learning Perl struck the right tone with me. It was interesting, had many quips unobtrustively in the footnotes, and kept a decent pace. It also pointed out several examples of good and bad Perl programming practices, which I appreciated (any fool can learn to program, it's programming well that takes time to learn).
The only headscratching chapter I found was Chapter 14: Process Management. It took me a couple of times reading the material to catch the gist of 'system' vs 'exec' and forking, etc. I just hope that the material comes more naturally when you need to use it. Other than that, I didn't have trouble following the material (a neccesary quality of any good learning manual).
In the next edition, I'd like to see some working examples in Appendix B: Beyond the llama. For instance, an example of perl used in a cgi context, and using perl to query a database (postgres or mySql, etc). Many of these topics are explored in other O'Reilly books, so I'd suggest taking a code sample and referencing the other book. I appreciate samplers because they get me interested in future learning directions.
In all, I rate the book a solid 7.