Perl module for persistent session data management

 Data::Session is typically used by a CGI script to preserve state data between
 runs of the script. This gives the end user the illusion that the script never
 exits.
 .
 It can also be used to communicate between 2 scripts, as long as they agree
 beforehand what session id to use.
 .
 See Data::Session::CGISession for an extended discussion of the design changes
 between Data::Session and CGI::Session.
 .
 Data::Session stores user data internally in a hashref, and the module
 reserves key names starting with '_'.
 .
 The current list of reserved keys is documented under "flush()". Of course,
 the module also has a whole set of methods to help manage state.