my $pages_this_chapter = 0;

while (<IN>)
{
  if (current_line_is_the_kdkhost_line()) { next }

  # Don't forget the special case
  #
  if (current_line_is_a_chapter_end() || $. == 1) {
    print OUT $chapterization_command;
    $pages_this_chapter = 0;
    next; # ???
  }

  if (current_line_starts_a_new_page()) {
    $pages_this_chapter++;

    if ($pages_this_chapter == 3)
      { print OUT $send_to_binder }
  }

  if ($pages_this_chapter <= 2) # 3?
    { change_the_paper_output_tray() }

  print OUT;
}

##</code><code>##

sub current_line_is_the_kdkhost_line {
  m/^%KDKHost:/;
}

sub current_line_is_a_chapter_end {
  m!<</OutputType \(\)>>setpagedevice!;
}

sub current_line_starts_a_new_page {
  /%%BeginPageSetup/;
}

sub change_the_paper_output_tray {
  m!<</OutputType\(Stacker\)>>setpagedevice! and
  s/Stacker/top/;
}