anchor.diff:      leaves _!
   ;
   
  -: (?do)  ( start-limit -- start-limit start!=limit )
  -    d# 0 over=
  -;
  -
   header-imm ?do
   :noname
       do-common
  -    ['] (?do) compile,
  -    tif leave, tthen
  -    tbegin
  -    inline: >r
  +    inline: dup
  +    leave,
  +    dotail
   ;
   
   \ Finish compiling DO..LOOP
  
positive.code: header-imm do
  :noname
      do-common
      tbegin
      inline: >r
  ;
  
negative.code:     here h# 2000 w,
  ;
  
  header-imm then     ( addr -- )
  : tthen
      here 2/
      swap +!
  