(cont.) INITIAL_SP holds the initial Stack Pointer value so
that we know where to reset it on ABORT

CURRENT points to the last dict entry.

HERE points to current write offset.

IP is the Interpreter Pointer

FLAGS holds global flags. Only used for prompt output control
for now.

PARSEPTR holds routine address called on (parse)

CINPTR holds routine address called on C<
                                                        (cont.)