use Var::Pairs;

sub countdown {
    my $n = shift;

    return sub {
        return if $n < 0;  # Indicates iterator exhausted
        return $n--;       # Next value iterated
    }
}

for my $limit (reverse 1..5) {
    while (my ($a) = each_value countdown($limit)) {
        print $a, ':';
    }
    say q{};
}

##</code><code>##

for my $limit (reverse 1..5) {
    my $iter = countdown($limit);
    while (my ($a) = each_value $iter) {
        print $a, ':';
    }
    say q{};
}