my $r = {
   field1 => [qw( black blue red )],
   field2 => [qw( black      red )],
   field3 => [qw(       blue     )],
};

...  change $r->param(...) to $r->{...} ...

my $row_num = 0;
printf("   %-6s %-6s %-6s\n", @array_pos);
printf("   %-6s %-6s %-6s\n", ('-'x6)x3);
foreach my $row (\@field1, \@field2, \@field3) {
   printf("%d: ", $row_num++);
   foreach my $col (0..2) {
      printf("%-6s ", $row->[$col]);
   }
   print("\n");
}

   black  blue   red
   ------ ------ ------
0: black  blue   red
1: black         red
2:        blue