for my $a (0,1) {
   for my $b (0,1) {
      print "Quadrant $a,$b:\n";
      for my $i (0,1) {
         for my $j (0,1) {
            my $row = 2*$a + $i;
            my $col = 2*$b + $j;
            print "  element $i,$j => matrix coord $row, $col\n";
         }
      }
   }
}