my $start= BuildKey( $xBand, $yBand, $Z1-$R1-$M );
    my $end=   BuildKey( $xBand, $yBand, $Z1+$R1+$M );
    ... "select * from shapes where key between $start and $end"
    my $record;
    while(  $record= Fetch( ... )   ) {
        if(  Overlap( $record, ... )  ) {
            Report( ... );
            return 1;
        }
    }
  }
}
return 0;