The effect on the hash is indistinguishable, as far as I can say. But the two expressions have different values: %hash = () returns an empty hash, whereas undef %hash returns undef. This isn't a big deal, but in my opinion big enough to keep the two distinct.

In reply to Re^3: '%hash = ()' is slower than 'undef %hash' by haj
in thread '%hash = ()' is slower than 'undef %hash' by rsFalse

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