PStore implements a file based persistence mechanism based on a Hash. User code
can store hierarchies of Ruby objects (values) into the data store file by name
(keys). An object hierarchy may be just a single object. User code may later
read values back from the data store or even update data, as needed.

The transactional behavior ensures that any changes succeed or fail together.
This can be used to ensure that the data store is not left in a transitory
state, where some values were updated but others were not.

Behind the scenes, Ruby objects are stored to the data store file with Marshal.
That carries the usual limitations. Proc objects cannot be marshalled, for
example.