my %info;
    while (<>) {
        my ($time, $id, $state) = parse_me ($_);
        unless ($info {$id}) {
            next unless $state eq 'open';
            $info {$id} = [$state, $time, 0];
            next;
        }
        if ($state eq 'open') {
            next unless $info {$id} -> [0] eq 'open';
            $info {$id} -> [0] = 'open';
            $info {$id} -> [1] = $time;
            next;
        }
        next unless $info {$id} -> [0] eq 'open';
        # This means the previous state was "open", and the current
        # state is "hold" or "closed". Increment the time.
        $info {$id} -> [2] += $time - $info {$id} -> [1];
        $info {$id} -> [0]  = $state;
        $info {$id} -> [1]  = $time;  # Not really needed.
    }

    # Finally, for all "open" cases, add the time since it went   
    # "open" till now.
    my $time = time;
    while (my ($id, $info) = each %info) {
        next unless $info -> [0] eq 'open';
        $info -> [2] += $time - $info -> [1];
    }