my $child = fork;
if (!$child)
{
  exec('someprogram.exe');
  exit;
}
else
{
  while (child_process_still_running())
  {
   sleep 1;
   system('kill -USR1 $child'); #signal child
   get_new_std_out_lines_child_has_printed_inresponse_to_signal();
  }
}