anchor.diff:  
   (defun externals-clasp-expand (argv)
     (format t "~%Extracting archive:~A~%" (opt "download.archive"))
  -  (when (and (probe-file (merge-pathnames (format nil "lib/~A/~A/externals-clasp/~A" (uname-m) (uname) (getf argv :version))
  +  (when (and (probe-file (merge-pathnames (format nil "lib/~A/~A/externals-clasp/~A/success" (uname-m) (uname) (getf argv :version))
                                             (homedir)))
                (not (opt "install.force")))
       (format t "~A/~A is already installed. add 'install.force=t' option for the forced re-installation.~%"
  
positive.code:                 ,(decide-download 'externals-clasp-download)
                  externals-clasp-expand
                  externals-clasp-make
                  ))))
  
negative.code:   (setf (config "externals.clasp.version") (getf argv :version))
    (cons t argv))
  
  (defun externals-clasp-sentinel (argv)
    (with-open-file (i (merge-pathnames (format nil "lib/~A/~A/externals-clasp/~A/success" (uname-m) (uname) (getf argv :version))
                                        (homedir))
                       :direction :probe
                       :if-does-not-exist :create))
    (cons t argv))
  
  (defun externals-clasp-help (argv)
    (format t "~%")
    (cons t argv))
  