(let (pre-playpen-package playpen-package)

  (defun enter-playpen ()
    (setf pre-playpen-package *package*)
    (locks:without-package-locks
      (setf playpen-package
	    (make-package :playpen-package
			  :use '(#:cl #+sbcl #:sb-alien #+sbcl #:sb-debug #+sbcl #:sb-ext
				 #+sbcl  #:sb-gray #+sbcl #:sb-profile #:utils)))
      (setf *package* playpen-package)))

  (defun leave-playpen ()
    (locks:without-package-locks
      (setf *package* pre-playpen-package))
    (delete-package playpen-package)))