macro_rules! test_arrow {
    ($x:expr => $y:expr) => {
        println!("{} {}", $x, $y);
    };
}
macro_rules! test_comma {
    ($x:expr, $y:expr) => {
        println!("{} {}", $x, $y);
    };
}
fn main() {
test_arrow!("hello" => 2 + 2);
test_comma!("hello", 2 + 2);
}