use constants TIMEOUT => 50;
use constants wbemErrTimedOut => 0x80043001;

while (1) {
   $o1 = $h1->NextEvent(TIMEOUT);
   ProcessEvent1($h1, $o1) if ($o1 != wbemErrTimedOut);

   $o2 = $h2->NextEvent(TIMEOUT);
   ProcessEvent2($h2, $o2) if ($o2 != wbemErrTimedOut);
}