sub relpath {
  my ($from, $to) = @_;
  my @f = split '/', $from;
  my @t = split '/', $to;

  while (@f and @t) {
    shift(@f), shift(@t), next if $f[0] eq $t[0];
    return join '/', ("..") x @f, @t;
  }

  return "./";
}