perl doesn't release thread memory

Dear Group,

I've made a simple stufy regarding memory deallocation and threads with 
ActivePerl 5.8.6;
This simple script taken from the documentation takes up infinite memory. 
Anyone sees any problem, or knows a workaround?

use threads;
my $thr;

for (;;) {
 $thr = threads->new(\&sub1);
 $thr->detach();         # bug also present with $thr->join()
 sleep 1;
}
sub sub1 {  print "In thread!\n"; }

Another interesting issue is that adding an explicit undef clears up memory 
...
for (;;) {
 $thr = threads->new(\&sub1);
 $thr->detach();         # bug also present with $thr->join()
 undef $thr;                # crazy attempt
 sleep 1;
}

and works with the sample script, but with my complicated program, it fails 
with some ugly messages
Win32::OLE(0.1702): GetOleObject() Not a Win32::OLE object at 
C:/Perl/site/lib/Win32/OLE/Lite.pm line 221.
Win32::OLE(0.1702): GetOleObject() Not a Win32::OLE object at 
C:/Perl/site/lib/Win32/OLE/Lite.pm line 221.
Win32::OLE(0.1702): GetOleObject() Not a Win32::OLE object at 
C:/Perl/site/lib/Win32/OLE/Lite.pm line 221.
Win32::OLE(0.1702): GetOleObject() Not a Win32::OLE object at 
C:/Perl/site/lib/Win32/OLE/Lite.pm line 154.
Can't call method "Refresh" on an undefined value at 
module/base/DataService.pmline 122.
Attempt to free non-existent shared string 'Open', Perl interpreter: 
0x224014 at (eval 1) line 1.
Attempt to free non-existent shared string 'State', Perl interpreter: 
0x224014 at (eval 1) line 1.
Free to wrong pool 223f50 not ab35988 at (eval 1) line 1.

This is disturbing. If perl is not deallocating memory naturally, I suppose 
that there is some internal reference
to the thread. But the thread is supposed to be detached! That's strange 
thing #1;

Strange thing #2 : On the other hand, when I explicitly undef $thr, and perl 
deallocate it, that means $thr was the only reference to
the thread object. But if that is true, why in the first place didn't perl 
deallocate the thread object when I overwrote the
reference with a new thread?

Thanks in advance. I look forward to hear a bit of the wisdom and experience 
of the more experienced perl programmers from this list

My best regards,
Gabriel