anchor.diff:        (null
          (isys:%sys-getenv name))
         (environment
  -       (%getenv/obj env name)))))
  +       (%obj-getenv env name)))))
   
   (defun (setf environment-variable) (value name &key env (overwrite t))
     (let ((value (string value))
  
positive.code:               (length keys)
                (car keys) (lastcar keys)))))
  
  (declaim (inline %getenv/obj %setenv/obj %unsetenv/obj))
  
  (defun %getenv/obj (env name)
    (gethash name (environment-variables env)))
  
  (defun %setenv/obj (env name value overwrite)
    (when (or overwrite
              (not (nth-value 1 (%getenv/obj env name))))
      (setf (gethash name (environment-variables env))
            value)))
  
  (defun %unsetenv/obj (env name)
    (remhash name (environment-variables env)))
  
  (defun environment-variable (name &key env)
  
negative.code:       (null
         (isys:%sys-setenv name value overwrite))
        (environment
         (%obj-setenv env name value overwrite)))
      value))
  
  (defun makunbound-environment-variable (name &key env)
  