properly use {} in rust

ex.rs

fn main() {
  struct House { owner: Box<Person> }
  struct Person { age: int }
  let mut house = box House {
    owner: box Person {age: 30}
  };
  
  { // this pair of braces is required
    // here the brace is the operator, it release the reference
    // awesome !!!
    let mut age= &mut house.owner.age;
    *age += 10;
  }

  print!("{}\n", house.owner.age);  // 40
}