anchor.diff:                  (member handler (disabled-handlers hook) :test #'equals))
         (if append
             (alexandria:appendf (symbol-value hook) (list handler))
  -          (pushnew handler (handlers hook) :test #'equals)))))
  +          (pushnew handler (handlers hook) :test #'equals)))
  +    hook))
   
   (declaim (ftype (function ((or handler symbol) list) (or handler boolean)) find-handler))
   (defun find-handler (handler-or-name handlers)
  
positive.code:        (defclass ,hook-class-name (hook)
           ((handler-class :initform ',handler-class-name)))
         (defmethod add-hook ((hook ,hook-class-name) (handler ,handler-class-name) &key append)
           ,(format nil "Add HANDLER to HOOK.
  HOOK must be of type ~a
  HANDLER must be of type ~a."
                    hook-class-name
  
negative.code: ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  (defun add-hook-internal (hook handler &key append)
    "Add HANDLER to HOOK if not already in it.
  Return HOOK.
  HANDLER is also not added if in the `disabled-handlers'.
  If APPEND is non-nil, HANDLER is added at the end."
    (serapeum:synchronized (hook)
  