I would disagree with calling a Perl module a "black box". Maybe a "dark box", "light grey box", or a "cream box", depending on one's knowledge of Perl. Remember, with all Perl code the source is available for you to examine - and even modify if you wish. For someone wishing to learn about a new aspect of Perl, seeing how one welliimplemented solution approached a problem is an excellent way to learn.
Oh yeah! If I had a dime for every new concept or nifty trick I learned from poking around in someone else's module code, well I'd be eatin' steak instead of ramen.... 8)