use strict;
use warnings;

use Algorithm::Loops qw( NestedLoops );

my @arr = qw( A B C D E F );
my $N   = 2;

my $i = NestedLoops([
   [ 0 .. @arr ],
   ( sub { [ $_ .. @arr ] } ) x ($N-1)
]);

while (my (@positions) = $i->()) {
   my @tmp = @arr;
   splice(@tmp, $_, 0, 'N') for reverse @positions;
   print(join(',', @tmp), "\n");
}