pub fn main(world: World) -> Void raises {
    var bytes: [9]u8 = [122, 101, 114, 111, 32, 108, 97, 110, 103]
    var index: usize = 0
    while index < 4 {
        let saved: u8 = bytes[index]
        bytes[index] = bytes[index + 5]
        bytes[index + 5] = saved
        index = index + 1
    }
    if bytes[0] == 108 as u8 && bytes[1] == 97 as u8 && bytes[2] == 110 as u8 && bytes[3] == 103 as u8 && bytes[4] == 32 as u8 && bytes[5] == 122 as u8 && bytes[6] == 101 as u8 && bytes[7] == 114 as u8 && bytes[8] == 111 as u8 {
        check world.out.write("word reverse ok\n")
    }
}