The Dark Side of Tom Bombadil

[The Might]

This is relative and depends on what you consider perfect.
If you consider it a sign of evil and imperfection that Tom would be likely to throw away the Ring somewhere if he would be given it to guard and would not understand its importance, thus putting all the dwellers of Middle-earth in danger, then I guess he is not perfect.
But as he is not of Middle-earth, I personally believe he doesn't have anything to really do with it. He has his own "realm" and is Master within its boundaries. Any evil he would perhaps commit would never be intended, but just the consequence of his origin.