anchor.diff:  
   (defun shared-instance (key)
     (with-lock-held ((message-lock *global-controller*))
  -    (gethash key *shared-instances*)))
  +    (gethash key (shares *global-controller*))))
   
   (defgeneric (setf shared-instance) (val key)
     (:method (val key)
  -    (setf (gethash key *shared-instances*) val)))
  +    (with-lock-held ((message-lock *global-controller*))
  +      (setf (gethash key (shares *global-controller*)) val))))
  
positive.code:   (setf (controller-thread controller)
          (make-thread #'controller-loop
                       :name "CONTROLLER MESSAGE LOOP"
                       :initial-bindings `((*shared-instances* . ,*shared-instances*)
                                           (*global-controller* . ,controller)))))
  
  (defun controller-loop ()
    (let* ((controller *global-controller*)
  
negative.code: (in-package :verbose)
  
  (defvar *global-controller* NIL)
  
  (defclass controller (pipeline)
    ((thread :accessor controller-thread)
     (shares :initform (make-hash-table) :accessor shares)
     (message-condition :initform (make-condition-variable :name "MESSAGE-CONDITION") :reader message-condition)
     (message-pipe :initform (make-array '(10) :adjustable T :fill-pointer 0) :accessor message-pipe)
     (message-lock :initform (make-lock "MESSAGE-LOCK") :reader message-lock))
  