# Iterate over all sets
for my $set1_k (keys %matrix) {
 
    # Iterate over points in this set
    for my $point1_k (keys %{$matrix{$set1_k}}) {

        # Iterate over sets this point's entry refers to
        for my $set2_k (keys %{
                                $matrix{$set1_k}
                                ->{$point1_k}
                             })
        {

            my $filename = join("", $set1_k, "v", $set2_k, ".xls");
            # TODO: Create the Excell file.

            # Iterate over points in that set
            for my $point2_k (keys %{
                                    $matrix{$set1_k}
                                    ->{$point1_k}
                                    ->{$set2_k}
                                   })
            {

                # TODO: Populate the Excell file
                # The data that you'd want to write to the Excell
                # file is accessable under
                # $matrix{$set1_k}->{$point1_k}->{$set2_k}->{$point2_k}
                # in this loop.

            }

            # TODO: if necessary (check module docs): close Excell file
        }
    }
}