I think that assigning a slice to the empty list is probably as good as it gets. 

@saw{@in} = ();
@out = keys %saw;

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The recently-seen-here, undef @saw{@in}; may be as fast, but it doesn't really sing out its intent.

After Compline,
Zaxo

In reply to Re: better union of sets algorithm? by Zaxo
in thread better union of sets algorithm? by perrin

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