in reply to
Iterating over Blocks of 2-Dim Array

Algorithmically, you can think of this as a tensor product of 2 2x2 matrices. In code, you could represent this as

`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";
}
}
}
}
`

If you wanted to convert in the opposite direction, just use the inverse equations:

`for my $row (0..3) {
for my $col (0..3) {
print "Quadrant ", int($row/2),',',int($col/2);
print " Element ", $row % 2,',', $col % 2,"\n";
}
}
`

Update: added inverse operation.