fn tail(text: String) -> Span<u8> {
    return text[1..]
}

fn suffix(text: String) -> String {
    return text[1..]
}

pub fn main(world: World) -> Void raises {
    let view: Span<u8> = tail("zero")
    let text: String = suffix("zero")
    if std.mem.len(view) == 3 && view[0] == 101 && std.mem.eql(text, "ero") {
        check world.out.write("string param span slice ok\n")
    }
}