> A claim is just a list of "AND" conditions, i.e. all the conditions must be met for the claim to be asserted. To defeat a patent claim, it's a matter of adding enough variance in your code to defeat ONE of the conditions.

That's not true. Thanks to the doctrine of equivalents you can still infringe on a patent even if your invention differs from what the claim describes. (Now, if you want your invention to count as prior art, it does have to exactly match the claim - whether two inventions are considered the same for prior art purposes is different from whether they're considered the same for infringement purposes.)