Jerry D. Hedden has already answered to my bug report. He states that:
(...)it's not an OIO bug. It's a problem with the perl interpreter and/or threads::shared.
He managed though to fix this in new OIO version that he ut on CPAN (1.71):
http://cpansearch.perl.org/src/JDHEDDEN/Object-InsideOut-3.71/Changes

Thank you all for help and thanks to Jerry for quick reaction!

In reply to Re^2: Object::InsideOut leaks memory when using threads::shared by menth0l
in thread Object::InsideOut leaks memory when using threads::shared by menth0l

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