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

my $next = iter_powerset( 1,2,3,4,5 );
while ( my @combo = $next->() ) {
    print "@combo\n";
}

sub iter_powerset {
    my @factor = @_;
    my $end = $#factor;
    my @subset = (undef) x $end;
    my ($pos, $mode) = (-1, 1);
    my $return = sub { return @factor[ grep defined, @subset ] };
    my %dispatch = (
        1 => sub {
            ++$pos;
            $subset[ $pos ] = $pos;
            ++$mode if $pos == $end;
            $return->();
        },
        2 => sub {
            $subset[ $pos - 1 ] = undef;
            ++$mode;
            $return->();
        },
        3 => sub {
            $subset[ $pos-- ] = undef;
            while ( $pos >= 0 ) {
                last if defined $subset[ $pos ];
                --$pos;
            }
            $subset[ $pos++ ] = undef;
            return () if ! $pos;
            $subset[ $pos ] = $pos;
            $mode = 1;
            $return->();
        },
    );
    return sub { $dispatch{ $mode }->() };
}