sub kv_for_largest_v {
    my $hr = shift;
    return undef unless keys %$hr;
    my ($k,$v) = each %$hr;
    my @rv = ([ $k, $v ]);
    while (my ($k2,$v2) = each %$hr) {
        if ($v2 > $rv->[0][1]) {
            # New maximum value, reset the list
            $rv =  ([ $k2, $v2 ]);
        }
        elsif ($v2 == $rv->[0][1]) {
            # Another copy of the max distance, add to the list
            push @rv, [ $k2, $v2 ];
        }
    }
    return \@rv;
}