sub inc
{
    my ($next) = @_;

    my ($hours, $mins, $secs) = split /:/, $next;
    $mins += 10;

    if ($mins >= 60)
    {
        ++$hours;
        $mins -= 60;
    }

    return sprintf '%02d:%02d:%02d', $hours, $mins, $secs;
}

##</code><code>##

$next = inc($next);