I am a new user of the threads feature in Perl 5.8.8. I am invoking a subroutine five times and appear to be getting all the desired output in a common directory. Each thread generates a uniquely named set of output files. I get the following message for three stings such as 'Documents' and the a crash: Attempt to free non-existant shared string 'Documents' , Perl interpreter: 0x23865fc during global destruction. The reference to 'Documents' apparently comes from the following line of code: my $doc = $app->Documents->Open($infname); which accesses some functionality using a design automation interface. I used the following sequence after starting up all the threads. # Loop through all the threads foreach my $thr (threads->list) { # Don't join the main thread or ourselves if ($thr->tid && !threads::equal($thr, threads->self)) { $thr->join; } sleep 2; } Can somone please help?