pub fn main(world: World) -> Void raises {
    var out: [6]u8 = [0_u8; 6]
    let actual: Maybe<Span<u8>> = std.str.reverse(out, "drawer")
    if actual.has {
        if std.mem.eql(actual.value, "reward") {
            check world.out.write("reverse string ok\n")
        }
    }
}