Beginners:
Programming Perl by Larry Wall, Tom Christiansen, Jon Orwant
*www.perl.org/books/beginning-perl/ (Beginning Perl by Simon Cozens)
Learning Perl - Randal Schwartz and Tom Phoenix
Advanced Users:
Mastering Perl By Brian Foy
Advanced Perl Programming By Simon Cozens
Professional Perl and MySQL (Professional Perl and MySQL)
For trials:
Wicked Cool Perl Scripts By Steve Oualline