$User {
    unique String name
}

$User.name() -> String {
    return self.name
}

@Greeter { }

@Greeter.sayHello(String toWhom) -> String {
    $User u = $User[name: toWhom]
        else create $User{} then {
            return f"Hello new user {toWhom}"
        }
    return f"Hello registered user {u.name()}"
}