Quick, what does
$ perl -wle 'sub A::a{1}; @B::ISA='A'; sub B::a{$_[0]->SUPER::a}; print B->a;'
do? I'm betting you didn't expect it to do:
Can't locate object method "a" via package "main" at -e line 1.
Hmm...
I think I found a bug. And if it's not classed as a bug then it damned well should be, since it makes it next to impossible to do some neat stuff (without implementing a SUPER.pm or something of that ilk).
Time to patch the appropriate test file in the perl source and submit my first patch to p5p.