You're looking for the intersection between the sets of keys in both hashes. So, something like this should work: 
my %common;
$common{$_}++ for keys(%hash1), keys(%hash2);

my @common = grep { $common{$_} > 1 } keys %common;

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In reply to Re: HoH and accumulation by dragonchild
in thread HoH and accumulation by djbiv

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