Module Algorithm::Combinatorics has a subsets subroutine.

#!/usr/bin/perl

# http://perlmonks.org/?node_id=1212655

use strict;
use warnings;

my $draw = 2;
my $from = 3;

my $pattern = '(2+?)' x $draw;
(2 x $from) =~ /^$pattern(??{print "@+[1..$draw]\n"})/;
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Excuse my thickness, but why do we need 2 here? It works equally well with 0, 3, 4, etc., or with characters like a, b etc., but it doesn't work with 1. Why's that?

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
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Because the print returns 1, and we need the (??{...}) block to return something that does not match, to cause the regex engine to backtrack.

your answer is in the tartaglia's triangle aka pascal one

              n!
 C(n,k) =  ----------
            k!(n-k)!
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is the basic formula to get your answer. To get some code search for tartaglia and pascal here at the monastery or look here.

If you want a module you can look at Math::Combinatorics too

L*

How did you search? I have Algorithm::FastPermute, Algorithm::Permute, Combinatorial::Permutations, List::Permutor, List::Permutor::Repeat, Permute::Named, and sevaral in Math::Permute::*.

From the example given it would appear that Cody Fendant is actually after Combinations rather than Permutations. Your point about searching is still valid, of course.

Update: A quick search of my own resulted in Short survey of modules for combinations and permutations which is another possibility of a good starting point.

If I understand you correctly, this is the basic example of NestedLoops from Algorithm::Loops:

use Data::Dumper;
use Algorithm::Loops 'NestedLoops';

my $depth = 6;
my $range = 40;

NestedLoops( [[1..$range], ( sub { [$_+1..$range] } ) x ($depth-1)], s
+ub { print Dumper \@_})
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If you want to create all those pairings in memory, NestedLoops can also give you the list instead of invoking a callback.