sub nearest {
    my $num = shift;
    my $firstlen = int(length($num)/2 + .5);
    my $first = substr($num, 0, $firstlen);
    my $back = reverse($first);
    substr($back, 0, 1, '') if $firstlen > length($num)/2;
    # Update (again): if higher, check lower and vice-versa:
    my $one = $first . $back;

    $first += $one < $num ? 1 : -1;
    $back = reverse($first);
    substr($back, 0, 1, '') if $firstlen > length($num)/2;
    my $two = $first . $back;

    return abs( $one - $num ) < abs( $two - $num)  ? $one : $two;
}