my@a=([],[],[],[],[],[],[],[],[],[]);

print_2D_array(@a);

my$a=-1;map{@$_=(++$a)x$a}@a;

print_2D_array(@a);

map{map{print "-",$_}@$_;print"\n"}@a;

sub print_2D_array {
    my $count;
    for my $ref (@a) {
       my @inner_array = @$ref;
       print "Elements of level ".$count++." ";
       for(@inner_array) {print "$_-"}
       print "\n";
    }
    print "\n";
}

print "\n\nDon't be a square\n\n";

my@a=([],[],[],[],[],[],[],[],[],[]);
my$a=-1;map{@$_=('no')x10}@a;
map{map{print "-",$_}@$_;print"\n"}@a;