Here in America a "poor mans copyright" simply will not do. If someone else took your song, and took the time to regester it with the copyright office, there is no way your simple work on paper would hold up in a court of law. Not even the ol' send it to yourself via register mail would save you. If you do not register it, you have NO PROTECTION WHAT SO EVER. There is no if and or buts about it, but hey, it's your work. Do with it as you will.