I learned Perl from the manuals. The first Perl book I bought
was long after I considered myself experience - it was the
second edition of the Camel, and I only bought it because my
employer was going to pay for it.
Currently, I have a shelf full of Perl books. I'd say I got
30% for free, 50% I bought at YAPC actions and the remaining
20% I bought. Only a few books I read completely (most of
them because of reviewing), others I only read parts or browsed through them. I'd say that a third of the Perl books
I own, I've never looked into yet.
That doesn't mean I don't prefer books in general. But I know Perl already so I've no reason to look into learning
Perl books, I don't see the point of books of the form
"Perl and X", and, most of all, I know where to find things
in the manual. That doesn't mean I think the manual is perfect, far from that. But with the Camel, I always think,
what does this book have that the manual doesn't? Furthermore, I'm not at all thrilled about the quality of
the Perl books. There are a lot of bad books, there are a
bunch of so-so books, a couple of average books, and very
few good books. I don't know any excellent of gem Perl books. It's striking that the book I find most useful for
a Perl programmer doesn't contain anything about Perl.
It's Stevens' Advanced Programming in the UNIX Environment.