FunkyMonk that is great stuff, I rewrote the bitvector to make it a lot faster.

    bit_vector2 => sub {

        my $vec1 = Bit::Vector->new(1000001);
        $vec1->Index_List_Store(@searched);
        my $vec2 = Bit::Vector->new(1000001);
        $vec2->Index_List_Store(@to_find);
        my $vec3 = Bit::Vector->new(1000001);
        $vec3->And($vec1, $vec2);
        
        my @present = $vec3->Index_List_Read();

        return 0+@present;
    },
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