column name does not exist

Hi All,

I have created a stored procedure

CREATE OR REPLACE FUNCTION ab(integer, integer,varchar,text,integer) RETURNS
text AS'
DECLARE
ret text;
BEGIN
if(ret is null) then
raise notice ''invalid auxiliary tag'';
end if;
return ret;
END;
'LANGUAGE 'plpgsql';

On doing: select * from ab (1,4,"exam","abhi",5);

I get an error : ERROR: column "exam" does not exist.

Any idea what is going wrong? Am I missing something?

Thanks in Advance
Abhinav