And as you already have an ePub version, I would like to suggest selling it (or giving it away free, as you already do) in the iBookStore as well. iPad is an amazing device for reading technical books, and I spend few hours every day reading ePub books in iBooks.app (I read Crockford's book and 3 other O'Reilly books just in the past 2 months).

Right now there are many Perl books in the iBookStore, but they're mostly cookbooks (step-by-step tutorial), not a no-bullshit introduction to the language as your book is! I'm sure many many more would discover or benefit from your book if it was available there as well :)