my $r = undef;
my %codes = ( 'hour' => $notifytable_hour,
              'hfhour' => $notifytable_hour << 1 + ( $notifytable_min > 29 ? 1 : 0 ),
              'qhour' => $notifytable_hour << 2 + floor( $notifytable_min / 15 ),
              'minute' => $notifytable_min,
              0 => $notifytable_min );
if ( exists($codes{$rdg}) ) {
    $r = $codes{rdg};
}