I'm not sure what you're trying to do. But if you're using SQL Developer, you don't need to add || ';' ||. Just use the csv comment:
with rws as (
select rownum x, 'stuff' y from dual connect by level <= 5
)
select /*csv*/x as "heading 1", y as "heading 2" from rws;
"heading 1","heading 2"
1,"stuff"
2,"stuff"
3,"stuff"
4,"stuff"
5,"stuff"