use strict;
use warnings;
use feature 'say';

use PadWalker qw/ closed_over set_closed_over /;
use Algorithm::Combinatorics qw/ combinations_with_repetition /;

my @data = qw( a b c );
my $state;

{   
    say "\tDay one, hard work ahead...";
    my $iter = combinations_with_repetition( \@data, 3 );
    say @{ $iter-> next } for 1 .. 5;

    say "\tEnough work for one day!";
    $state = closed_over( $iter );
}
{
    say "\tDay 2, back to work...";
    my $iter = combinations_with_repetition( \@data, 3 );

    $iter-> next;   # init

    set_closed_over( $iter, $state );

    say "\tDeadline! Exhaust the iterator!";
    while ( my $c = $iter-> next ) { say @$c }
}

__END__

>perl comb.pl
        Day one, hard work ahead...
aaa
aab
aac
abb
abc
        Enough work for one day!
        Day 2, back to work...
        Deadline! Exhaust the iterator!
acc
bbb
bbc
bcc
ccc


##</code><code>##

use strict;
use warnings;
use feature 'say';

use Algorithm::Combinatorics qw( combinations_with_repetition );

package Algorithm::Combinatorics {

no warnings 'redefine';

sub main::combinations_with_repetition {
    my ($data, $k, $ref) = @_;
    __check_params($data, $k);

    return __contextualize(__null_iter()) if $k < 0;
    return __contextualize(__once_iter()) if $k == 0;

    my @indices = $ref ? @$ref : (0) x $k;
    my $iter = Algorithm::Combinatorics::Iterator->new(sub {
        __next_combination_with_repetition(\@indices, @$data-1) == -1 ? undef : [ @{$data}[@indices] ];
    }, [ @{$data}[@indices] ]);

    my $x = __contextualize($iter);  # Note: scalar context forced
    return [ $x, \@indices ]         # + interface changed
}
}
 
my @data = qw( a b c );
 
my ( $iter, $secret ) = 
    @{ combinations_with_repetition( \@data, 3 )};

say @{ $iter-> next } for 1..5;

my ( $iter_2 ) = 
    @{ combinations_with_repetition( \@data, 3, $secret )};

say '**********';

$iter_2-> next;     # skip 1
while ( my $p = $iter_2-> next ) { say @$p }

__END__

aaa
aab
aac
abb
abc
**********
acc
bbb
bbc
bcc
ccc