use Win32::Mutex;
$mut = Win32::Mutex->new(0);
...
fork_the_children;
...
#and then in the children use
...
$mut->wait();
$nfound = select($rout=$rin, $wout=$win, $eout=$ein, undef);
$mut->release();
...

#!!! you should preven the mutex from being destroyed by
# any of the children. It should only be destroyed by the
# main thread and only after all children finished !!!

 ... # just before a child thread finishes
 bless $mut, 'do not destroy';
}