Flyweight Pattern in The Portland Pattern Repository could be a good starting point. In particular, I see that this link inside the page also points to interesting "stories" of usage of the pattern, which could help you get it better.
One thing to watch out for when people use the term "flyweight" in the Perl community is that they are sometimes using it as TheDamian used it in his excellent Perl OO book, which was in a slightly different way from the GoF defined it. See Flyweights - different meaning in perl? for gory details.
