anchor.diff:        (null
          (isys:%sys-unsetenv (string name)))
         (environment
  -       (%remvar env name))))
  +       (remhash name (environment-variables env)))))
     (values name))
   
   (defun environment ()
  
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:   ((variables :initarg :variables
                :initform (make-hash-table :test #'equal)
                :accessor environment-variables)))
  
  (defun environment-variable (name &key env)
    "ENVIRONMENT-VARIABLE returns the environment variable
  