in reply to using / accessing nested hash/array references
are not equivalent. You have encountered a context issue, the first line above is list context, the second is scalar, in other words, $hostresults is not an array as I think you are expecting. I think what you would want to do is change the second line to something like:
@results = &get_list();
$hostresults = &get_list();
Then $hostresults is a reference to your first data set.
$hostresults[$i] = \@results;
You might want to look at perldsc and perlref