substr($str, 0, $pos1) = '';

##</code><code>##

  print $indent x $depth, substr( $str, 0, $pos1, '' );

##</code><code>##

  my $_consume = sub {
    print $indent x $_[2], substr $_[0], 0, $_[1], '';
  }

  sub pp {
    return unless @_;
    my($str) = @_;
    my($length, $first) = f1($str);

    if (!defined $first) {
      $_consume->($str, $length, $depth);
    } elsif ($first eq CONST1) {

##</code><code>##

      $_consume->($str, $length + 1, --$depth);
    } elsif (defined(my $newlen = f2($str, $first))) {
      $_consume->($str, $newlen + 2, $depth);
    } else {
      $_consume->($str, $length, $depth++);
    }
    return $str;
  }