Thread1-

  lock($signal);
  eval {
    local $SIG{ALRM} = sub { die "alarm\n" };
    alarm 30;
    cond_wait($signal);
    alarm 0;
  };

  if ($@) {
     print "timed out\n";
  }else{
     print "did not time out";
  }


Thread 2;

cond_signal($signal);