present: i32?: some 1
absent: i32?: nil
success: i32 ! str: ok 1
failure: i32 ! str: err 'failed'
piped: i32?: some 4->double
grouped: i32?: some {4->double}

double :: @ value { value * 2 }
describe :: @ (label: str, count) -> str { label }

unwrap_or: i32? -> i32: @ value {
    match value {
        some inner => inner
        nil => 0
    }
}

handle: i32 ! str -> i32: @ result {
    match result {
        ok value if value > 0 => value
        ok _ => 0
        err message => message->length
    }
}