Oracle PLSQL Array - Build Column Names For Query

CREATE OR REPLACE PROCEDURE DOARRAY AS
    PREFIX VARCHAR2(1) := 'a';
    q_str varchar2(2000) := '';
    total_cols integer ;
    /************  only change this : define a new array *******************/
    type col_array IS VARRAY(5) OF VARCHAR2(100);
    col_nms col_array := col_array('name', 'resrce_id', 'addr', 'home_phn', 'mobile_phn');
 
BEGIN
    total_cols := col_nms.count;
    FOR i in 1 .. total_cols LOOP
      case
        when (i=1) then
          q_str := PREFIX || '.' || col_nms(i) || ',';
        when (i=total_cols) then
           q_str := q_str || PREFIX || '.' || col_nms(i);
        else
           q_str := q_str || PREFIX || '.' || col_nms(i) || ',';
      end case;
   END LOOP;
   dbms_output.put_line('Query String: ' || q_str);
END DOARRAY;