( $collapse_idx[0]{$cur_row_ids{3}} //= $_[0][$result_pos++] = [] ),
( ( ! defined $cur_row_data->[0] ) ? $collapse_idx[0]{$cur_row_ids{3}}[1]{"books"} = [] : do {
+ ( ! $collapse_idx[1]{$cur_row_ids{0}} )
+ and
push @{$collapse_idx[0]{$cur_row_ids{3}}[1]{books}},
$collapse_idx[1]{$cur_row_ids{0}} = [ { owner => $cur_row_data->[1], title => $cur_row_data->[0] } ]
- unless $collapse_idx[1]{$cur_row_ids{0}}
} ),
}