$ cargo run
     Locking 1 package to latest compatible version
      Adding closure-example v0.1.0 (/Users/chris/dev/rust-lang/book/tmp/listings/ch13-functional-features/listing-13-05)
   Compiling closure-example v0.1.0 (file:///projects/closure-example)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.43s
     Running `target/debug/closure-example`
Before defining closure: [1, 2, 3]
After calling closure: [1, 2, 3, 7]