If instead of using array indexes you use the actual array values is saves the bother of having to save the current outer loop value. Anonymonk makes a useful point about meaningful variable names.

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

for my $iter ( 1 .. $iters )
{
    for my $num ( @nums )
    {
        for my $ltr ( @ltrs )
        {
            say qq{$num$ltr};
        }
    }
}'
1a
1b
1c
2a
2b
2c
3a
3b
3c
1a
1b
1c
2a
2b
2c
3a
3b
3c
$
[download]

Another way to do this would be to localise the list separator and use glob and the list multiplier in a do block.

$ 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
$
[download]

I hope this is of interest.