foreach $line (@lines) { 
  ($time, $id, $open) = parse($line);
  next until $code eq 'open';
  $open = $time;

  until ($code eq 'hold') {
  $line = shift(@lines);
  ($time, $id, $code) = parse($line);
  $total += $time-$open;
}

##</code><code>##

while (@lines) { 
  $line = shift(@lines);
  ($time, $id, $code) = parse($line);
  $hash{$id}{want} ||= 'open';
  next unless ($hash{$id}{want} eq $code);

  if ($code eq 'open') {
    $hash{$id}{open} = $time;
    $hash{$id}{want} = 'hold';
  } else { 
    $hash{$id}{total} += $time - $hash{$id}{open};
    $hash{$id}{want} = 'open';
    delete $hash{$id}{open};
  }
}