$ perl -Mstrict -Mwarnings -E '
my @nums = qw{ 1 2 3 };
my @ltrs = qw{ a b c };
my $iter = 2;

say for do {
   local $" = q{,};
   ( glob qq{{@nums}{@ltrs}} ) x $iter;
   };'
1a
1b
1c
2a
2b
2c
3a
3b
3c
1a
1b
1c
2a
2b
2c
3a
3b
3c
$