I learned from reading the first edition of
Programming Perl, but I had already
been programming for many years.
If you are new to programming, I suggest
that you have a look at
Perl and CGI for the World Wide Web by Liz Castro. It
has a lot fewer technical errors than most
introductory Perl books aimed at beginning
programmers, and it's also much thinner, which I think is an advantage. Once you
have the basics down you can move to a more advanced and comprehensive reference like
Programming Perl.