Expiry plug-in for Memoize that adds LRU cache expiration

 Memoize::ExpireLRU implements an expiry policy for Memoize that follows LRU
 semantics, that is, the last n results, where n is specified as the argument
 to the CACHESIZE parameter, will be cached.
 .
 For the theory of Memoization, please see the Memoize module documentation.