# cycle through 16 x and 16 y values,
# which generate a total of 256 tile indexes
for $y ( 0..15 ) {                           
    for $x ( 0..15 ) {
        # this calculates the tile index we are currently at,
        # using the x and y coords in this block
        $tile_index = $y+($x*16);            
        
        # this calculates the real x and y values of this tile
        $rx = ($bx*16)+$x;                   
        $ry = ($by*16)+$y;
        
        # insert type data into the internal map array and 
        # note that there was change in this block if applicable
        if (
            !defined $tiles[$rx][$ry][$bz][type] ||
            $tiles[$rx][$ry][$bz][type] != $type_data[$tile_index]
        ) {
            $changed = 1;
            $tiles[$rx][$ry][$bz][type] = $type_data[$tile_index];
        }
    }
}