1) Sure, but realize that a cache is meant to be transitory. It's not where you should be keeping anything you really care about like an order or something where losing cache data might mean losing money. Some of the caches engines are less likely than others to dump data on their own. IIRC, FileCache is one of the ones that is not going to do it.

2) Of course.

3) $user is just going to be something like "Egil Kveldulfr." Or better, a user id, like 1005. It's just a unique key (or it's not safe because a user might see another user's cache data) for the user. The $customer is just some theoretical data object, like a DBIx::Class object of a customer account and its related data like orders.

That is a working example you gave, I think. You just need to fill in the data. I'd try something more simple to start... Oh, I see mortiz just replied. His advice is good: play with the test files.