You are mistaken. The cache object accessible by $self->cache() (where $self is the Command) is the same cache used by the application (and your suggested $self->app->cache() would, if it were supported, do exactly the same thing -- access the cache shared by both the Application and the Command). Once again, the cache is shared state. It is not a "component" of the Application, but rather an instance variable (a reference to the Cache object) kept in both Application and Command.
in reply to Re^2: scripting frameworks - a cursory glance
in thread scripting frameworks - a cursory glance
It would make no sense for "application object components" to be accessed via the cache (regardless of the syntax used to access the cache). The cache stores whatever a user wants to share (like a logging or a database object), not internal CLI::Framework data.
If you're reading the code, then yes, the Cache class happens to be implemented inside the Application module (mainly because the existing Cache class is trivially simple and may later be replaced by a more powerful caching system like CHI; I decided it is unworthy of its own module at this stage). But that doesn't make it a "component" of the Application class.