SQL & PL/SQL

This query works fine:

WITH x(xd) AS 
 (SELECT 'Aa,Bx,D,Z' FROM dual)
SELECT XMLType('<rows>'||
         XMLQuery('for $k at $l in ora:tokenize($str,",") 
                   return  <a>{$k}</a>'
           PASSING xd as "str"  
           RETURNING CONTENT)||
          '</rows>') xd 
  FROM x;

XD                                                                        
---------
<rows>                                                                    
  <a>Aa</a>                                                               
  <a>Bx</a>                                                               
  <a>D</a>                                                                
  <a>Z</a>                                                                
</rows>  

I'm trying to make the tags dynamic <a1></a1>, <a2></a2>, but this isn't so easy:

WITH x(xd) AS 
 (SELECT 'Aa,Bx,D,Z' FROM dual)
SELECT XMLType('<rows>'||
         XMLQuery('for $k at $l in ora:tokenize($str,",") 
                   return  <a{$l}>{$k}</a{$l}>'
           PASSING xd as "str"  
           RETURNING CONTENT)||
          '</rows>') xd