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

use Data::Dumper;


my @array = qw(1 2 3 4 5);

my $potenz = P(\@array);

print Dumper($potenz);



sub P{
  my ($arrayref) = @_;
  my $potenzmenge = [];
  my $base = [[]];
  my $bool = 1;
  my $length = 0;
  while($bool){
    push(@$potenzmenge,@$base);
    $base = calc_elems($base,$arrayref,$length);
    $length++;
    $bool = 0 if($length > scalar(@$arrayref))
  }

  return $potenzmenge;
}


sub calc_elems{
  my ($base,$arrayref,$length) = @_;
  my @array = @{$arrayref};
  my @new_elems = ();

  foreach my $base_elem(@$base){
    foreach my $index($length..(scalar(@array) - 1)){
      my @tmp_elem = @{$base_elem};
      last if($tmp_elem[-1] && ($tmp_elem[-1] >= ($array[-1])) &&
$length > 0);
      next if($tmp_elem[-1] && (($tmp_elem[-1] == $array[$index]) ||
$tmp_elem[-1] > $array[$index]));
      push(@tmp_elem,$array[$index]);
      push(@new_elems,[@tmp_elem]);
    }
  }

  return \@new_elems;
}