Learning Perl the Hard Way
This is a book for people who already know how to program in another language, but don't know Perl. The book gets through the basics as quickly as possible and emphasizes good programming style in Perl. It also focusses on object-oriented programming in Perl.
The book is released under the GNU Free Documentation License. Readers are free to copy, modify and distribute the text. This allows the book to be adapted to different needs and help develop new study material.
The book is available in a variety of electronic formats: LaTeX, PDF, Postscript and online HTML version.