Check out "Perl Best Practices" by Damien Conway, and the more recent "Modern Perl" by Chromatic. Both can be had as paperbacks, and I think both are also available free on online.
It has so many great pieces of advice that apply to any programming task, everything from naming variables, to testing, error handling, code organization, documentation, etc, etc. Ultimately, for timeless advice on programming as a profession the language is immaterial.