This defines the policy for file I/O with modules such as
File::Slurp::WithinPolicy. The purpose is to allow systems administrators
to define locations and restrictions for applications' file I/O and give
app developers a policy to follow. Note that the module doesn't ENFORCE the
policy - application developers can choose to ignore it (and systems
administrators can choose not to install their applications if they do!).

You may control which policy gets applied by creating a
File::Policy::Config module with an IMPLEMENTATION constant. You may write
your own policy as a module within the File::Policy:: namespace.

By default (if no File::Policy::Config is present), the
File::Policy::Default policy gets applied which doesn't impose any
restrictions and provides reasonable default locations for temporary and
log files.