my %animals;

for my $state ( keys %bighash ) {
    for my $zoo ( keys %{ $bighash{$state} } ) {
        $animals{ $bighash{$state}{$zoo}->[1] }->[0]->{$state}->{$zoo}
+++;
        $animals{ $bighash{$state}{$zoo}->[1] }->[1]++;
    }
}

for my $animal ( keys %animals ) {
    next unless $animals{$animal}->[1] > 1;
    for my $state ( keys %{ $animals{$animal}->[0] } ) {
        print "$state\n";
        for my $zoo ( keys %{ $animals{$animal}->[0]->{$state} } ) {
            print "ZOO: $zoo ANIMAL: $animal\n";
        }
        print "\n";
    }
}
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