Thanks for your enlightenment. I've been playing with perl -Dm compiled with -DDEBUGGING but I don't know yet how to make sense of the address it prints, or how do they map to perl data structures. 
0x81cdb38: (01225) malloc 28 bytes
0x81cf880: (01226) malloc 28 bytes
0x81cdb58: (01227) malloc 40 bytes
0x81ce210: (01228) malloc 16 bytes
0x81c2560: (01229) free

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Also I've found that the offending modules, although the objects I create inside the loop, are scoped inside the loop, so the object should be destroyed each loop iteration, as it happens with my test modules: 
new Test
DESTROY Test
new Test
DESTROY Test
new Test

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I have found the problem in Mail::Audit. It was a circular reference: 
#   $self->{obj} = $self; # backwards-compatibility for everyone who d
+esperately needed access to $self

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Taking that line out solves the problem. I'll send a notice to the author. Your insight has been very useful. Thanks.

In reply to Re^2: Abnormal memory in some modules by piotr
in thread Abnormal memory in some modules by piotr

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