In pure Perl, yes. In XS, it should be possible to iterate through the entire region of memory and see if anything has a valid reference. Also (and I'm stretching my memory here), isn't there a way in C to find out all the malloc'ed areas? You could compare that with the list of all reachable objects and see if there's a discrepancy...

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/me wants to be the brightest bulb in the chandelier!

Vote paco for President!