anchor.diff:          else
             collect clause))
   
  -(defun expand-case-macro (cont expr clauses &key (default-keys '(t otherwise)) error)
  +(defun expand-case-macro (cont expr clauses
  +                          &key (default-keys '(t otherwise)) error
  +                               (macro-name 'custom-case))
     (check-type clauses list)
     (when (eql error t)
       (setf error 'case-failure))
  
positive.code:               ,@macro-body)
              ,expr ,clauses
              :default-keys ',default-keys
              :error ',error))))))
  
  (defun clauses+default (clauses &key (default-keys '(t otherwise)))
    (let ((default-clause-tails
  
negative.code:                        (rec rest-clauses
                              dest-acc
                              (cons (first clauses) clauses-acc))
                         (let* ((sym (gensym (format nil "~a-~a" macro-name 'fn)))
                                (dest (cons sym body))
                                (body (list (funcall jump sym))))
                           (rec rest-clauses
  