our $can_foo;
is not as good as
my $can_foo;
There's no need for a package variable here.

MyPackage->can("foo");
is not as good as
__PACKAGE__->can("foo");
Less redundancy means smaller chance to make an error.

I had written this solution before coming up with the one I posted. I couldn't see any advantages to it, so I only included it in my post in comment tags.