for (my $i=0; $i < @array1; $i++)   {

    $dna = reverse $array1[$i];
    $dna =~ tr/actg/tgac/;

    if ($dna eq $array1[$i])   {

# problem is here, I am testing for equality, but need to test for complementarity!

           print "\nFOUND $array1[$i] \t $dna";
    }
}