Very simple to define and you can nest or contantenate them as needed.

module foo {
    fn bar() {
        std::print("Hello from foo::bar");
    }
}

module bar::baz {
    fn qux() {
        std::print("Hello from bar::baz::qux");
    }
}

/// you can also extend modules AS long as they are in the same file
module foo {
    fn baz() {
        std::print("Hello from foo::baz");
    }
}

fn main() {
    foo::bar();
    bar::baz::qux();
    foo::baz();
}