two solutions which try to avoid any modulo or printf:

  DB<198> for my $row (0..7) {
           for my $col (0..7) {
            print "$row/$col\t"
           }
           print "\n"
          }

0/0    0/1    0/2    0/3    0/4    0/5    0/6    0/7    
1/0    1/1    1/2    1/3    1/4    1/5    1/6    1/7    
2/0    2/1    2/2    2/3    2/4    2/5    2/6    2/7    
3/0    3/1    3/2    3/3    3/4    3/5    3/6    3/7    
4/0    4/1    4/2    4/3    4/4    4/5    4/6    4/7    
5/0    5/1    5/2    5/3    5/4    5/5    5/6    5/7    
6/0    6/1    6/2    6/3    6/4    6/5    6/6    6/7    
7/0    7/1    7/2    7/3    7/4    7/5    7/6    7/7    

  DB<199> for my $row (0..7) {
           for my $col (0..7) {
            print $row*8+$col,"\t"
           }
           print "\n"
          }

0       1       2       3       4       5       6       7       
8       9       10      11      12      13      14      15      
16      17      18      19      20      21      22      23      
24      25      26      27      28      29      30      31      
32      33      34      35      36      37      38      39      
40      41      42      43      44      45      46      47      
48      49      50      51      52      53      54      55      
56      57      58      59      60      61      62      63
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