Use GNU licenses with "or later" clause in Software::License

 Software::License::OrLaterPack allows one to use GNU licenses with
 "or later" clause where Software::License style license names are
 supported.
 .
 All "or later" are just subclasses of corresponding base license
 classes. For example, Software::License::GPL_3::or_later is a
 subclass of Software::License::GPL_3, so any "or later" license can
 be used like any other license. For example, in your dist.ini file:
 .
   license = GPL_3::or_later
 .
 However, licenses in the pack introduce few features not found in
 base classes.