How to reverse a string using arrays in oracle?

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DECLARE
   str VARCHAR2(100) := 'Hello World';
   str_length NUMBER := LENGTH(str);
   reversed_str VARCHAR2(100);
   i NUMBER := 1;
   arr dbms_sql.VARCHAR2A;
BEGIN
   -- Convert string to array
   FOR j IN 1..str_length LOOP
      arr(j) := SUBSTR(str, j, 1);
   END LOOP;

   -- Reverse the array
   FOR j IN REVERSE 1..str_length LOOP
      reversed_str := reversed_str || arr(j);
   END LOOP;

   dbms_output.put_line('Original String: ' || str);
   dbms_output.put_line('Reversed String: ' || reversed_str);
END;
/