Why use a tied hash when a normal old hash will do just fine? Store your numbers as the keys.
Math::TrulyRandom generates numbers from interrupt timing discrepancies. It's pretty slow. Generally you should just use it to seed your pseudo random number generator. You might want to have a look at EGD - the Entropy Gathering Daemon.
Thanks for your reply. The tied hash would be used because this program would run as a cron job and therefore would not know which numbers the previous run had generated.