# I have not figured out this part yet.
  #    elsif (ref($old) eq 'ARRAY' && ref($new) eq 'ARRAY') {
  #    }

##</code><code>##

sub deep_data_compare {
  
  my ( $old, $new ) = @_;

  if (ref $old eq 'ARRAY' && ref $new eq 'ARRAY') {

    #  Handle the case of uneven number of elements in
    #  each array reference as you see fit. Here assumption
    #  is that both references have the same number of
    #  elements.
    for my $ix ( 0 .. $#{ $old } ) {

      deep_data_compare( map $_->[ $ix ], $old, $new )
    }
  }

  ...
}