if ( $x > 10 ) {
    $query = '(select Name from Customers where CustId=?)'
    $cust_sth = $dbh->prepare( $query );
    $cust_sth->execute( $custid );
} else {
    $query = '(select Name from Sales where SalesId=? and SalesTerritory=?)'
    $sales_sth = $dbh->prepare( $query );
    $sales_sth->execute( $salesid, $territory );
}