About the `:variable' keyword in `define-minor-mode'

[Xue Fuqiao]

In the docstring of `define-minor-mode':

  [...]
  :variable PLACE [...]
                PLACE can also be of the form (GET . SET), where GET is
                an expression that returns the current state, and SET
                is a function that takes one argument, the new state,
                and sets it.

I don't understand the meaning of GET.  The docstring says it returns
the current state, but where will it return?

-- 
Best regards, Xue Fuqiao.
http://www.emacswiki.org/emacs/XueFuqiao