anchor.diff:         (%obj-unsetenv env name)))
       name))
   
  -(defun clear-environment (&key env)
  +(defun clear-environment (&optional env)
     "Removes all variables from an environment."
     (etypecase env
       (null
  
positive.code:       (environment
         (%obj-getenv env name)))))
  
  (defun (setf environment-variable) (value name &key env (overwrite t))
    (let ((value (string value))
          (name (string name)))
      (etypecase env
  
negative.code:        (%obj-setenv env name value overwrite)))
      value))
  
  (defun makunbound-environment-variable (name &optional env)
    "Removes the environment variable identified by NAME from the
  current environment.  NAME can be either a string or a symbol.
  Returns the string designated by NAME.  Signals an error on
  