Operators
The ever-friendly Tizag.com explanation: http://www.tizag.com/perlT/perloperators.php
The more formal Perlop re. Operators
Compare Perl vs. Shell Operators: http://localhost/index.php?option=com_content&view=article&id=208:operators-wildcards-expressions&catid=7:shell-scripting&Itemid=2786