Yaclml

ATTRIBUTE-BIND 

(defstruct (runtime-attribute-list-reference (:conc-name ralr-))
  (form nil))

This macro serves the same purpose as destructuring-bind but allows for a different syntax.

(define-condition tag-related-error (error)
  ((tag :accessor tag :initarg :tag :initform nil)))

(define-condition unrecognized-attribute (tag-related-error)
  ((attribute :accessor attribute :initarg :attribute))
  (:report (lambda (c s)
             (if (tag c)
                 (format s "Unrecognized attribute ~S in ~S." (attribute c) (tag c))
                 (format s "Unrecognized attribute ~S." (attribute c))))))

(define-condition illegal-attribute-use (tag-related-error)
  ((attribute-type :accessor attribute-type :initarg :attribute-type))
  (:report (lambda (c s)
             (format s "Attributes of type '~A' are not allowed ~A (hint: missing &allow-custom-attributes?)."
                     (attribute-type c)
                     (aif (tag c)
                          (format nil "for tag ~A" it)
                          "here")))))