sub build_inversion_list_and_index {
  my @invlist;
  my $match;
  for (0..$max_codepoint) {
    next unless $match xor (chr($_) =~ /[[:$class:]]/);
    push @invlist, $_;
    $match= !$match;
  }
  my @index= ( 0 );
  for (my $i= 0; $i < @invlist; $i+= 2) {
    push @index, $index[-1] + $invlist[$i+1] - $invlist[$i];
  }
  shift @index;
  return \@invlist, \@index;
}