use strict;
use warnings;

my $M = 5;
my @a = 1..$M;
my $N =  3;

get_all_tuples ($N, [], @a);

sub get_all_tuples {
	my ($level, $valref, @a) = @_;
	if ($level <= 1) {
		print "@$valref $_\n" for @a;
	} else {
		while (@a) {
			my $i = shift @a;
			push @$valref, $i;
			get_all_tuples ($level-1, $valref, @a);
			pop @$valref;
		}
	}
}

##</code><code>##

$ perl N_among_M.pl
1 2 3
1 2 4
1 2 5
1 3 4
1 3 5
1 4 5
2 3 4
2 3 5
2 4 5
3 4 5

##</code><code>##

$ perl N_among_M.pl
1 2 3 4
1 2 3 5
1 2 3 6
1 2 3 7
1 2 3 8
1 2 3 9
1 2 3 10
1 2 4 5
...
5 7 9 10
5 8 9 10
6 7 8 9
6 7 8 10
6 7 9 10
6 8 9 10
7 8 9 10

##</code><code>##

$ time perl N_among_M.pl
167960

real    0m0.524s
user    0m0.499s
sys     0m0.015s