Macro unwrap_return::ok_unwrap_break

macro_rules! ok_unwrap_break {
    ($e:expr) => { ... };
}

Unwraps in the Ok case; breaks in the Result case.

Drops everything contained within Err.

 ok_unwrap_break!(expression)

is shorthand for

 match expression {
     Ok(ret) => ret,
     Err(_) => break
 }