> I've been staring at my track_blessings routine, and I can't see a reason why this override is not happening.
That's because you cannot override built-in functions
during runtime - when perl is _compiling_ this line:

bless $foo, "Bar";

it decides what op code to generate (in that case what function to
invoke). This happens at compile time. After that, when
you call your track_blessings() it is too late - the
calling of CORE::bless is already compilied and hardcoded
in the syntax opcode tree.