in PlPgSQL function, how to use variable in a "select ... into .. where " query

Hello,

In pl/pgsql (postgresql 8.01), how to use variables in select .. into .. 
command

CREATE OR REPLACE FUNCTION test(VARCHAR) RETURNS VARCHAR AS $$
DECLARE  var1                           ALIAS FOR $1;                            cm_tableName
tableA.col1%TYPE;  T1                              VARCHAR := 'sourceTable';  query_value               VARCHAR ;
 
BEGIN
  SELECT col2 INTO cm_tableName FROM  T1  WHERE col1 = var1 ;  EXECUTE query_value;
   RETURN cm_tableName;END;
$$ language 'plpgsql' IMMUTABLE STRICT;

select test('abc');

Failed.


Also, tried "SELECT col2 INTO cm_tableName FROM ||  T1  WHERE col1 =  || 
var1 " and
"SELECT col2 INTO cm_tableName FROM ||  T1 ||  WHERE col1 =  || var1"

Failed as well.

T1 and var1 both are variables, may I how to use variables in a "select 
... into " query please?

Thanks a lot,
Ying