Perl books

Programming Perl, 3rd ed. by Larry Wall, Tom Christiansen & Jon Orwant (O'Reilly)
If you are really keen on Perl, then the best book on the subject is the famous Camel Book. It never leaves my desk. However, it is very difficult to teach from, and is only recommended if you have good knowledge of programming already. You have been warned.

Perl by Example, 4th ed. by Ellie Quigley (Prentice Hall)
A good in-depth book with many examples. In many ways it is similar to "Programming Perl" and targets the same audience.

SAMS Teach Yourself Perl in 24 Hours, 3rd ed. by Clinton Pierce (SAMS)
A very nice beginner book - easy to read and understand. Daps a bit into modules, databases and CGI. The aquiring of Perl knowledge is structured differently from the course, but the book is still recommended.

Beginning Perl for Bioinformaticians, 1st ed. by James Tisdall (O'Reilly)
The book is written for bioinformaticians and uses relevant examples. However it jumps around in the various Perl subjects in a confusing manner and does not explain anything well. Not recommended.