anchor.diff:                       (character-offset point 1)
                        (when (zerop (decf depth))
                          (return point)))
  -                    ((multiple-value-setq (n pair) (syntax-start-block-string-p point))
  -                     (character-offset point n)
  -                     (unless (search-forward point (cdr pair))
  -                       (return nil)))
                       ((syntax-string-quote-char-p c)
                        (%skip-string-forward point))
                       ((syntax-fence-char-p c)
  
positive.code:               (return nil))
              (let ((c (character-at point 0))
                    n pair)
                (cond ((syntax-open-paren-char-p c)
                       (push c paren-stack)
                       (character-offset point 1)
                       (when (zerop (incf depth))
  
negative.code:     (let ((c (character-at point))
            n pair)
        (let ((point
                (cond ((multiple-value-setq (n pair) (syntax-start-block-string-p point))
                       (character-offset point n)
                       (if (search-forward point (cdr pair))
                           point
                           nil))
                      ((syntax-open-paren-char-p c)
                       (%skip-list-forward point 0))
                      ((or (syntax-symbol-char-p c)
                           (syntax-escape-char-p c))
  