my @are_equal = compare_arrays(\@a, \@b);
sub compare_arrays {
    my ($first, $second) = @_;
    my @tmp;
    no warnings; # silence spurious -w undef complaints
    #return 0 unless @$first == @$second;
    for (my $i = 0; $i < @$first; $i++) 
    {
        if ($first->[$i] eq $second->[$i])
        {
            push(@tmp,$first->[$i]);
        }
    }
    return @tmp;
}