detach method doesn't release memory (ithreads)

All:

I have a Perl program (v5.8.0 on Mandrake Linux 9.0) that spawns a new
thread each time a user logs in and then detaches the thread when the
login tasks are completed.  For example:

my $peer_thr = threads->create(\&send_comm_messages, $username)->detach;  

I did a memory test on the program and found that each time a user logs
in, the memory resources used by the thread (~3MB) are not released when
the thread detaches.  There are no calculations performed in the thread 
and no values are returned.

I would not expect that this should be the case and was curious if others
have had similar experiences.

Thank you for your thoughts.

Steve