Receiving mouse events in Blub Prolog

gistfile1.pl

sprite( X, Y ) :-
    sprite(S), 
    S.x <- X, S.y <- Y,
    paint(S,0x8888ff),
    spawn(( repeat, 
            receive(S,mouseMove,E),
            S.x <- E.stageX - 50,
            S.y <- E.stageY - 30 )).

paint(Sprite,Color) :- 
    G <- Sprite.graphics,
    G.clear(void),
    G.beginFill( Color, 1 ),
    G.lineStyle( 0, 0 ),
    G.drawEllipse( 0, 0, 100, 60 ),
    G.endFill(void).