#!/usr/bin/perl
use strict;
use warnings;

my @list = (1 .. 5);
my $take = 2;

comb_integral(\@list, $take);

sub comb_integral {
  my ($items, $group, $list, $next) = @_;
  $list ||= [];
  $next ||= 0;

  if ($group == 1) {
    my $prefix = join " ", @$list;
    print "$prefix $_\n" for @$items[$next..$#$items];
  } else {
    for my $i ($next..$#$items) {
      push @$list, $$items[$i];
# the next line is an alternate which elimates the use of push/pop
#comb_integral($items, $group - 1, [@$list, $$items[$i]], $i + 1);
      comb_integral($items, $group - 1, $list, $i + 1);
      pop @$list;
    }
  }
}