A "vault" is a typed, persistent store for values of arbitrary types. It's
like having first-class access to the storage space behind IORefs. The
data structure is analogous to a bank vault, where you can access different
bank boxes with different keys; hence the name. Also provided is a "locker"
type, representing a store for a single element.

WWW: https://github.com/HeinrichApfelmus/vault
