$ perl -Mstrict -Mwarnings -e '
    my $X_initial = "80";
    my $Y_initial = "80";
    my $MAX_X = 240;
    my ($cur_x, $cur_y) = ($X_initial, $Y_initial);
    for (0 .. 20) {
        if ($cur_x > $MAX_X) {
            $cur_x = $X_initial;
            $cur_y += $Y_initial;
            print "\n";
        }
        print "   \t$_:$cur_x/$cur_y";
        $cur_x += $X_initial;
    }
    print "\n";
'
   	0:80/80         1:160/80        2:240/80
   	3:80/160        4:160/160       5:240/160
   	6:80/240        7:160/240       8:240/240
   	9:80/320        10:160/320      11:240/320
   	12:80/400   	13:160/400      14:240/400
   	15:80/480   	16:160/480      17:240/480
   	18:80/560   	19:160/560      20:240/560