anchor.diff:                      (let ((str (string-left-trim '(#\space #\tab) line)))
                         (when (and (< 0 (length str))
                                    (eql #\! (aref str 0)))
  -                        (return `(shell-command ,(subseq str 1))))))))
  +                        (return `(shell-command ,(subseq str 1)))))
  +                    (return x))))
               (t
                (add-history-expr x)
                (return x))))))
  
positive.code:              (setq line
                     (concatenate 'string line " "
                                  (rl:readline :already-prompted t))))
              ((and (zerop count) (symbolp x) (not (null x)))
               (add-history line)
               (cond ((command-p x)
                      (return (call-command x (subseq line pos))))
  
negative.code:   (let ((line (rl:readline :prompt prompt)))
      (loop
        :with x :and pos
        :for error-p := nil :do
        (handler-case (setf (values x pos)
                            (read-from-string line nil))
          (error () (setq error-p t)))
  