package Cycle;
use warnings;
require Exporter;
@ISA = qw/Exporter/;
@EXPORT = qw/cycle MC_cycle/;
use strict;
use Carp;

sub cycle {  # based on Ovid's algorithm
    my $toggle = shift;
    my @items  = @_;
    unless ($toggle =~ /^\d+$/ and $toggle != 0 and @items) {
        my $me = (caller(0))[3];
        confess "Hey stupid, you are supposed to call me like this:\n",
                "\t$me(positive_integer, some_list)\nNot like this:\n";
    }
    my $count = 0;
    my $index = -1;
    return sub {
        $index++   if $count++ % $toggle == 0;
        $index = 0 if $index == @items;
        $items[$index];
    }
}

sub MC_cycle { # based on MeowChow's algorithm
    my ($repeat, @items, $index) = @_;
    return sub {
        $items[ int ($index++ / $repeat) % @items ];
    }
}
__END__

##</code><code>##

# case 1: using MC_cycle(0, @colors);
[jandrew:~]$ perl foo.pl 
Illegal division by zero at Cycle.pm line 29.


# case 2: using cycle(0, @colors);
[jandrew:~]$ perl foo.pl 
Hey stupid, you are supposed to call me like this:
        Cycle::cycle(positive_integer, some_list)
Not like this:
        Cycle::cycle(0, 'red', 'white', 'blue') called at foo.pl line 6