let name = "prod";
let count = 3;
// *** before: ***
println!("{} serves {} nodes", name, count);
println!("{0}: {1} and {0} again", name, count);
// *** in version 1.58: ***
println!("{name} serves {count} nodes");
println!("{name}: {count} and {name} again");
// an expression is still passed as an argument
println!("{} nodes", count * 2);