$VAR1 = {
          'book 1 by Author_name' => 'Author_name',
          'book 1 by new' => 'New_Author',
          'book 2 by Author_name' => 'Author_name'
        };
$VAR2 = {
          'Author_name' => [
                             'book 1 by Author_name',
                             'book 2 by Author_name'
                           ],
          'New_Author' => [
                            'book 1 by new'
                          ]
        };