let result = captures!("Event A: 123.45",
      r"FloatEvent: (d+)" => |x| MyEvent::FloatEvent(&x[1].parse.unwrap()),
      r"StringEvent: (.+)"  => |x| MyEvent::StringEvent(&x[1]),
    );

assert_eq!(result, MyEvent::FloatEvent(123.45));

macro_rules! captures {
    ( $test:expr, $re:expr ) => { None };
    ( $test:expr, $re:expr => $closure:expr, $( $re2:expr => $rest:expr, )* ) => {
        match Regex::new($re).unwrap().captures(line) {  // todo lazy static
            Some(caps) => $closure(caps),
            _ => captures!($test, $re, $( $re2, $rest, )*)
        }
    };
}