anchor.diff:  
      When `bar` has an index `baz`, it will be bound to `foo` and
      printed. If not, the print statement will not be executed."
  -  `((lambda (,(car var)) (when ,(car var) ,@body)) ,(cadr var)))
  +  `((lambda ,(make-vars (car var)) (when ,(make-test (car var)) ,@body)) ,(cadr var)))
   
   (defun make-setting (var) :hidden
     (if (= (n var) 2)
  
positive.code: (defun make-vars (x) :hidden
    (if (list? x) x (list x)))
  
  (defun make-binding (xs) :hidden
    (if (= (n xs) 1)
      (car xs)
  
negative.code:    since `nil` is falsey, evaluation does not continue."
    (cond
      [(empty? vars) `((lambda () ,@body))]
      [else `((lambda ,(make-vars (caar vars))
                (cond
                  [,(make-test (caar vars)) (when-let* ,(cdr vars) ,@body)]
                  [else nil]))
              ,(make-binding (cdar vars)))]))
  
  