user: id name
item: id name
cart: user item
 Tables user and item both have a primary key named id (i recommend you make this an auto incremented unsigned integer). The two fields in the cart table have their _id extensions removed because Class::DBI prefers them that way. They are still foreign keys associated with their respective tables' ids. With all of that out of the way, here is the (untested) code: 
package CART::user;
use base qw(CART::DBI);
__PACKAGE__->table('user');
__PACKAGE__->columns(All => qw(id name));
__PACKAGE__->has_many(items => [qw(CART::item item)]);

package CART::item;
use base qw(CART::DBI);
__PACKAGE__->table('item');
__PACKAGE__->columns(All => qw(id name));
__PACKAGE__->has_many(users => [qw(DVD::user user)]);

package CART::cart;
use base qw(CART::DBI);
__PACKAGE__->table('cart');
__PACKAGE__->columns(Primary => qw/user item/);
__PACKAGE__->has_a(user => 'DVD::user');
__PACKAGE__->has_a(item => 'DVD::item');

package main;

for my $user (CART::user->retrieve_all) {
   my $items = $user->items;
   print $user->name;
   print " has no items\n" and next unless $items;
   print "has these items:\n";
   print $_->name, "\n" for @$items;
}

[download]
Better late than never. ;)

jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)

In reply to Re: Many-to-many with Class::DBI by jeffa
in thread Many-to-many with Class::DBI by Anonymous Monk

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