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How can I get the unique keys from two hashes?

by faq_monk (Initiate)
on Oct 08, 1999 at 00:20 UTC ( #631=perlfaq nodetype: print w/ replies, xml ) Need Help??

Current Perl documentation can be found at perldoc.perl.org.

Here is our local, out-dated (pre-5.6) version:

First you extract the keys from the hashes into arrays, and then solve the uniquifying the array problem described above. For example:

    %seen = ();
    for $element (keys(%foo), keys(%bar)) {
        $seen{$element}++;
    }
    @uniq = keys %seen;

Or more succinctly:

    @uniq = keys %{{%foo,%bar}};

Or if you really want to save space:

    %seen = ();
    while (defined ($key = each %foo)) {
        $seen{$key}++;
    }
    while (defined ($key = each %bar)) {
        $seen{$key}++;
    }
    @uniq = keys %seen;

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