I don't know how enlightened or clever this is, but I follow a fairly strict pattern of behavior whenever I run up against a new problem; go to search.cpan.org and type in all the relevant keywords I can think of. Spending the time looking through the list usually quickly establishes if I'm contemplating a new wheel or at the very least, a better way to go about my new wheel.
Following links to modules from responses to perlmonks and other discussions is also helpful, since it at least exposes me to modules I might otherwise not even think about.
Having said all that, I've actually been criticized before for consistently recommending CPAN modules on a project... it seems anyone can download and install modules, but real code monkeys hand code everything. I backed away slowly, in case sudden movement caused the critical overload of this person's synapses.