Passing a String with special character as an input

Hi -

This is related to my earlier post. For the function I am passing
a string. But the string some time has a single quote inside the string like
"IT's a String Test" , How can I handle that, can you please help?

CREATE OR REPLACE FUNCTION test_repl(x character varying)
RETURNS character varying AS
$BODY$
DECLARE
ret_var varchar(4000);
a record;
begin
ret_var := x;

for a in select * from lookup
loop
ret_var := replace(ret_var,a.code,a.codeword);
end loop;
return ret_var;
END;
$BODY$
LANGUAGE 'plpgsql' VOLATILE
COST 100;
ALTER FUNCTION test_repl(character varying) OWNER TO postgres;