That is indeed the goal I am working towards, but a bit more relaxed than Erlang: mutability is possible only within a single actor/thread, but anything sent in

That is indeed the goal I am working towards, but a bit more relaxed than Erlang: mutability is possible only within a single actor/thread, but anything sent in a message to another actor is deep copied. So no memory is ever shared, but the language allows single-threaded mutation for performance.