#!/usr/bin/perl -w
use strict;

sub combo 
{
	my ($k, $array_orig) = @_;
	my @array = @$array_orig; # copy
	my @set;
	if ($k == 1) {
		@set = map { [$_] } @array;
	}
	else {
		for (0 .. (scalar(@array) - $k)) {
			my $head = shift @array;
			push @set, map { [$head, @$_] }
				@{&combo($k - 1, \@array)};
		}
	}
	return \@set;
}

# 実行例 1
print join("\n", map { join(", ", @$_) } @{&combo(3, [1 .. 5])}), "\n\n";

# 実行例 2
print join("\n", map { join(", ", @$_) } @{&combo(3, ["a", "b", "c", "d"])}), "\n\n";

# 実行例 3
my $i = 1;
for my $s (@{&combo(6, [1 .. 8])}) {
	print $i++, "\t", join(", ", @$s), "\n";
}