foreach $ip (@ip_addresses) {

   $ip_address = $ip;

   if ($pool==0) {
        print "Main thread has no service threads available, yielding\n";
        threads->yield until $pool>0;
   }

   print "Main thread has $pool service threads available\n";

   # signal that a new line is ready
   {
     lock $pool;
     cond_signal $pool;
   }

   print "Main thread sent signal, waiting to be signaled\n";

   # wait for whichever thread wakes up to signal us
   {
     lock $ip_address;
     cond_wait $ip_address;
   }

   print "Main thread received signal, reading next line\n";


}