$all_cats = $dbh->selectall_arrayref("SELECT category_id,name FROM $sql{catego
  +ries} WHERE parent=$parent_cat_id ORDER BY category_id");

##</code><code>##

@categories = (
               {
                 id   => <i>insert category_id value here</i>,
                 name => <i>insert name value here</i>
                 level => <i>level (inside a category etc.) </i>
               },
               {
                 ...
               },
               ...
               );

##</code><code>##

$indent .= "&nbsp; ...";

##</code><code>##

$level++;

##</code><code>##

        foreach my $current_cat (sort { $a->[1] cmp $b->[1] } @{$all_cats}) {
              ($cat{id}, $cat{name}) = @$current_cat;
              push @main::categories {level=>$level,name=>$cat{name},id=>$cat{id}};
              &ListCategories($indent, $cat{id}, 'y');
          }