nom::alt!

macro_rules! alt {
    ($i:expr, $($rest:tt)*) => { ... };
}

try a list of parser, return the result of the first successful one

Incomplete results are ignored

 named!( test, alt!( tag!( "abcd" ) | tag!( "efgh" ) ) );
 let r1 = test(b"abcdefgh");
 assert_eq!(r1, Done(&b"efgh"[..], &b"abcd"[..]));
 let r2 = test(&b"efghijkl"[..]);
 assert_eq!(r2, Done(&b"ijkl"[..], &b"efgh"[..]));