anchor.diff:         (isys:%sys-setenv (string name) value overwrite))
         (environment
          (when (or overwrite
  -                 (null (nth-value 1 (%envar env name))))
  -         (setf (%envar env name) value)))))
  +                 (null (nth-value 1 (gethash name (environment-variables env)))))
  +         (setf (gethash name (environment-variables env))
  +               value)))))
     value)
   
   (defun makunbound-environment-variable (name &key env)
  
positive.code:       (null
         (isys:%sys-getenv name))
        (environment
         (%envar env name)))))
  
  (defun (setf environment-variable) (value name &key env (overwrite t))
    (let ((value (string value))
  
negative.code:       (null
         (isys:%sys-unsetenv (string name)))
        (environment
         (remhash name (environment-variables env)))))
    (values name))
  
  (defun environment ()
  