in reply to
When -w and use strict aren't enough...
Just as a new Perl programmer might get tired of hearing "use strict" or "use CGI", you're going to get tired of hearing "write tests" if you have a problem which testing tends to solve. Use Devel::Cover to develop a code coverage profile and you have a good start on writing your tests. I'll even help:
use Test::More 'no_plan';
my $module = 'Foo.pm';
use_ok($module) or die;
Then, just fill in "can_ok" stubs for your functions. As you uncover bugs, write a test that exploits them. It's not quite the same as test driven development, but I'm scratching my head trying to think of ways to get people to test who otherwise wouldn't :)