Convert varchar2 to LOB

Hi guys

I want to convert each of varchar2 row into single
clob.
--
declare
temp varchar2(4000);
my_lob clob;
cursor k
select row from any_table;
begin
open k;
loop
fetch k into temp;
exit when k%notfound;
dbms_lob.append(my_lob, temp);
end loop;
close k;
end;
--
But this not work, howto cast temp to lob??