anchor.diff:      (do () (nil)
         (unless (next-char 1)
           (return))
  -      (unless (and (syntax-escape-char-p (preceding-char))
  -                   (not (syntax-escape-char-p (char-before-2))))
  +      (unless (escape-p (preceding-char) (char-before-2))
           (when (eql (following-char) goal-char)
             (next-char 1)
             (return t))))))
  
positive.code:     (do () (nil)
          (unless (next-char 1)
            (return))
        (unless (and (syntax-escape-char-p (preceding-char))
                  (not (syntax-escape-char-p (char-before-2))))
          (let ((c (following-char)))
            (cond
             ((eql c paren-char)
  
negative.code:       (return))
      (let ((c (following-char)))
        (cond
         ((escape-p (preceding-char) (char-before-2)))
         ((not
           (or
            (syntax-escape-char-p c)
  