It partly depends on the resources available to you. If you have a computer, or reasonable access to one, Perl comes with extensive documentation. The Library section of the monastery here has copies of them, and you can find newer (and older!) versions at http://perldoc.com.
If you can obtain them, there are many, many books on Perl as well. A reasonably good set is represented in Buy Stuff. (The monastery also benefits if you buy through those links.) The usefulness of a book depends very much on your own likes and dislikes, however, so if you can, spend some time in a bookstore browsing.
Good luck. You have a fun journey ahead of you!
