This, because it might not be an unreclaimed object, most objects are consistant, but more of a forgotten re-initialised hash or something.

So i thought, by determing the size of the objects at different times i can localize the memory-monster.

I already wrote a global-variable-dump procedure that's useful in this case but i can't seem to determine the actual size of declared objects and used modules.

Q: Why did the Perlmonk cross the road?
A: He wanted to escape the match.

Well if I were me (and I am) I'd write something that uses B to account for at least the visible stuff. If that didn't work then some handy dandy XS code could walk the internals. I'm of course assuming you have already read the note in perldebguts on "Debugging Perl memory usage" and you need more detail... (if you haven't then obviously this is where you go first)