for(;;){
while ( <DHCP> ) { 

  # New ACK found. 
  # $macthreads{$mac} = new thread(\&launch, l_opts)


 }#while

  foreach $mac (keys(%macthreads)){
    if($macthreads{$mac}->is_joinable {
    $macthreads{$mac}->join;
    delete $macthreads{$mac};

  }

}#for