Have you ever heard of appending a borring story with the expression "and then I found five dollars"? Since the fifth element of the list of incoming parameters to a sub is represented by $_[4], and superficially looks like (to someone's mind who as not in Perl mode) like $4 (currency), and to someone who is partly in Perl mode and partly loopy from lack of sleep and coffee (and thought it would make a good joke) looks like $5(currency) since perl starts counting at 0, I thought it was ironic.

Actually, while I was typing this response, I got an e-mail from a seller on ebay that he had refunded me $4.99 worth of shipping charges (ironically not because the joke was bad, and the explanation boring).