A match expression is made up of arms. An arm consists of a pattern to match against, and the code that should be run if the value given to match fits that arm's pattern in turn.

let secret_number = rand::thread_rng().gen_range(1..=100);
let mut guess = String::new();
io::stdin()
    .read_line(&mut guess)
    .expect("Failed to read line");

match guess.cmp(&secret_number) {
    Ordering::Less => println!("Too small!"),
    Ordering::Greater => println!("Too big!"),
    Ordering::Equal => println!("You win!"),
}

Bind by reference with ref keyword

At first it seems a bit crazy that there's a keyword for this, but it's because using &Foo is a different type from Foo. So you need to use ref Foo if you want to match against Foo not Foo, but use a reference to actually unpack the value in your match arm.

let maybe_name = Some(String::from("Alice"));
// Using `ref`, the value is borrowed, not moved ...
match maybe_name {
    Some(ref n) => println!("Hello, {n}"),
    _ => println!("Hello, world"),
}
// ... so it's available here!
println!("Hello again, {}", maybe_name.unwrap_or("world".into()));