You only showed that Perl knows how it should call a function, not that the it knows how a function was called. Perl obviously has to know how to call a function (since one checks @ISA and the other doesn't), but that doesn't mean it keeps track of how a function was called. Despite your claim, you haven't shown me wrong (yet).

Update: I was unhappy with my original wording. I rephrased what I wrote to make more sense.