anchor.diff:       ,@(mapcar #'((x)
    	                (if (consp x)
   		     		    x
  -		     			(aif (assoc x *tagbody-replacements*)
  +		     			(aif (cdr (assoc x *tagbody-replacements*))
   		       				!
   		       				x)))
                  args)
  
positive.code:   `(vm-scope ,@(vars-to-identity body)))
  
  (defun lookup-create-gensym (block-name)
    (or (assoc block-name *blockname-replacements*)
        (with-gensym g
          (acons! block-name g *blockname-replacements*)
          g)))
  
negative.code:                       ,@(if (vm-jump? (car tail))
  						    tail
  						    `((%setq ~%ret ,@tail)))))
               (bname (cdr (assoc block-name *blockname-replacements*))))
          (if bname
              (nconc ret (list bname) '((identity ~%ret)))
              (nconc ret '((identity ~%ret)))))
  