if f == "" || len(f)%2 != 0 || strings.TrimLeft(f, "0123456789abcdef") != "" {
			return false
		}
	}
	return true
}

// It would be nice if the error messages always began with
// the standard file:line: prefix,
// but that's not where we are today.
// It might be at the beginning but it might be in the middle of the printed instruction.