. . .
my $query = qq(
       with recursive cte (comment_ID, comment_post_ID, comment_author, comment_parent,
                           comment_date_gmt, comment_type, comment_content) as (
            select     comment_ID,
                       comment_post_ID,
                       comment_author,
                       comment_parent,
                       comment_date_gmt,
                       comment_type,
                       comment_content
            from       wp_comments
            where      comment_ID = ? AND comment_approved = 1
            union all
            select     p.comment_ID,
                       p.comment_post_ID,
                       p.comment_author,
                       p.comment_parent,
                       p.comment_date_gmt,
                       p.comment_type,
                       p.comment_content
            from       wp_comments p
            inner join cte
                       on p.comment_parent = cte.comment_ID
       )
       SELECT *
              FROM cte ORDER BY comment_date_gmt;
    );
    my $sth = $dbh->prepare($query);
    $sth->execute($id);

    while(my $row = $sth->fetchrow_hashref) {
        my $cid       = $row->{comment_ID};
        my $parent_id = $row->{comment_parent};
        my $post_id   = $row->{comment_post_ID};

        if ($parent_id eq 0) {
            push(@{$posts{$post_id}}, $cid);
        }
        
        $comments{$cid}->{comment_post_ID}  = $row->{comment_post_ID};
        $comments{$cid}->{comment_parent}   = $row->{comment_parent};
        $comments{$cid}->{comment_author}   = $row->{comment_author};
        $comments{$cid}->{comment_date_gmt} = $row->{comment_date_gmt};
        my $content = $row->{comment_content};
        $content =~ s|(\s*)\n(\s*)\n|$1<br />\n$2<br />\n|gm;
        $comments{$cid}->{comment_content}  = $content;
        
        push (@{$hierarchy{$parent_id}}, $cid); 
    }

    $sth->finish();

. . .

##</code><code>##

sub render {
    my ($layer, $k, $comments, $hierarchy) = (@_);
    my $comment = $hierarchy{$k};
    if (!defined($comment)){
        return(0);
    }

    $layer++;
    my $ul = HTML::Element->new('ul');
    my $count = 0;
    foreach my $c (@{$comment}) {
        my $li = HTML::Element->new('li');
        $li->attr('id', "comment$c");
        my $p1 = HTML::Element->new('p');
        $p1->attr('class','author');
        $p1->push_content($comments{$c}->{comment_author} );
        $li->push_content($p1);
        
        my $p2 = HTML::Element->new('p');
        $p2->attr('class','date');
        $p2->push_content($comments{$c}->{comment_date_gmt});
        $li->push_content($p2);

        my $div = HTML::Element->new('div');
        $div->attr('class','words');
        $div->push_content($comments{$c}->{comment_content});
        $li->push_content($div);
        
        $ul->push_content($li);
        print "."x$layer,$c,"\n" if ($VERBOSE);
        my $html = &render($layer, $c, $comments, $hierarchy);
        if ($html) {
            $ul->push_content($html);
            $count++;
        }
    }
    return($ul);
}