sub could_be_a_host {
  my @a = split /\./, shift, -1;
  @a > 0 and
    not grep !/^[a-z0-9\-]+$/i, @a and
    not grep /^\d+$/, @a and
    not grep /^-|-$/, @a;
}

##</code><code>##

sub could_be_a_host {
  my @a = split /\./, shift, -1;
  return 0 unless @a;
  for (@a) {
    return 0 unless /^[a-z0-9\-]+$/i;
    return 0 if /^\d+$/;
    return 0 if /^-/;
    return 0 if /-$/;
  }
  1;
}