sub compare {
  return unless length $_[0] == length $_[1];

  # Omit if expecting differences almost all the time.
  return 1 if $_[0] eq $_[1];

  my $limit = 1;

  foreach (split('', $_[0]^$_[1])) {
     next unless ord;
     return 0 unless $limit--;
  }

  return 1;
}