In-place sorting would be much faster [ O(N log N) instead of O(N2) ] and can be be written to use O(1) extra memory. However, it destroys the original arrays.

Also, you're wasting memory by placing @c on the stack. You could drop your memory usage from O(N) to O(1) by compressing @c in-place. grep doesn't work in-place like sort when the source and destination is the same.

Update: Added downside.

In reply to Re^2: Difference arrays. by ikegami
in thread Difference arrays. by BrowserUk

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