'88959b2c541a8854042ef52b45af1075' => {
                                        'files' => [
                                                     {
                                                       'file_type' => 1,
                                                       'date_uploaded' => '2005-10-25',
                                                       'file_name' => 'Name of file.tif',
                                                       'date_faxed' => ''
                                                     },
                                                     {
                                                       'file_type' => 2,
                                                       'date_uploaded' => '2005-10-25',
                                                       'file_name' => 'some file 823144 N.pdf',
                                                       'date_faxed' => '2005-10-25'
                                                     }
                                                   ],
                                        'phone' => 'xxx-xxx-xxxx',
                                        'last_name' => 'Doe',
                                        'dme_num' => '123456',
                                        'old_file' => '2005-10-25',
                                        'dme_pid' => '938edfd95dd42a58786330bb8c85f479',
                                        'first_name' => 'John'
                                      },

##</code><code>##

foreach my $key (sort { $patients->{$a}->{old_file} cmp $patients->{$b}->{old_file} }
   (keys %{$patients})) {
      # print ...
}