Joost, the copy was done before the benchmark. Its the operations on the copied values that's slower. I assume perl is treating both as numbers because both have the IOK flag set which also means I think both have identical code paths. I think then, the only difference is that these values are spaced out more in memory and consume more memory. To code, I expect there should be no difference. In reality, the only thing I can guess is that it has something to do with CPU caches or any of that nonsense that I'm not sure how to reason about.