What does the poem sound like?

Just one comment:

"could of" is wrong, especially in written form. It's the corruption of "could've".

My thought exactly -- however, I'd like to clarify a bit and mention that the contraction comes from "could have". You see the same kind of thing with would have, should have, etc.

Also, I think the poem is very sweet.

Yep, I agree, "could have" is just fine, you don't really need a contraction. Just fix that, and it is a very touching poem indeed.

Ah, what you thought is different to my original guess, in which I secrectly assumed "could of" is a slang usage for "could have" that sweeps out the traditional grammar rule you guys emphasized in here -- that is, I guessed the usage works in poem (my appreciatory skill for poems is too weak )

Anyways, thanks for reply.

Thing is, the real corruption is from "could have" to "could've". It's a common if not pretty contraction.

ESL students frequently misunderstand it as "could of" but despite the sound no native speaker is really saying that.

Oh God, I've seen many native English speakers saying so -- "could of", even once I particularly asked an administrator of a big forum why he used "could of" when he posted his important thread in his front page -- he was a native English speaker. And those Americans, Brits, Aussies, Canadians etc. in his forum are used to the usage "could of". And who do you guess wrote the poem above? A native Brit, not me -- I cannot write that wonderful poem for the present at all.
But in my mind I accept the could have is normal which should be put in first place when writing.

OristarA is right -- "could of" is rampant in America! I think it's a misunderstanding because the pronounciation is so close to "could've"... but it's one of those things that's just wrong!

No matter how many people do it!