Now that I've found this and read it:
and now that I've strained my brain trying to figure out the crashes I've observed when interpreters are modperl_interp_unselect()ed, I'm pretty sure that PerlInterpScope doesn't work as documented. I think that interp pool cleanups get registered into the correct pool (maybe) but so many (if not all) modperl_interp_select() calls have matching modperl_interp_unselect() calls that the interp pool cleanups are redundant and the subject patch aborts them.
So my patch stops the crashes but doesn't result in correct PerlInterpScope behavior.
I also suspect that a better fix of this interpreter management might also get the other bug I'm chasing.
So I have a question: How important is this PerlInterpScope directive?
My node in the Web: http://www.kandarian.com