Short term

- come up with some decent benchmarks


Long term

- consider using an alternate shared memory backend, instead of
  IPC::Shareable.  IPC::Shareable is super convenient and well written, 
  but it deals with hashes and references and calls Storable itself, which
  is somewhat redundant and most of that functionality isn't used

- figure out a good mechanism for automatically and periodically 
  purging the cache of expired objects

- figure out a way to determine the current shared memory usage, and
  implement a way of keeping it under some constant
