reader

        Contains a code block to implement special READ behaviors for any
        GET.  If Get:reader contains a code block, READMODAL() evaluates that
        block to READ the GET (the Get object is passed as an argument to the
        block).  The block may in turn call any desired function to provide
        custom editing of the Get object.  If Get:reader does not contain a
        code block, READMODAL() uses a default read procedure (GetReader())
        for the Get object.

        Note that Get:reader allows particular Get objects to have
        specialized READ behaviors without changing the standard READMODAL()
        function.  This preserves compatibility for GETs which are to be
        handled in the customary way and also eliminates potential conflicts
        between different extensions to the GET/READ system.