Actors [ :Helloer :Goodbyer :Worlder :Changer ] ;

Every :Tick :Helloer  does [ Say "Hello, "   ] ;
Every :Tick :Goodbyer does [ Say "Goodbye, " ] ;
Every :Tick :Worlder  does [ Say "World!"    ] ;
Every :Tick :Changer does [
    Peek :CurrentScene ; Is :HelloWorld ; Then [
        Become :GoodbyeWorld ; Done ;
    ] ;

    Peek :CurrentScene ; Is :GoodbyeWorld ; Then [
        Become :HelloWorld ; Done ;
    ] ;
] ;

Scenes [ :HelloWorld :GoodbyeWorld ] ;

When :HelloWorld :Started do [
    Create Helloer ;
    Create Worlder ;
    Create Changer ;
] ;

When :GoodbyeWorld :Started do [
    Create Goodbyer ;
    Create Worlder ;
    Create Changer ;
]

Enter HelloWorld ;