def exists?(key, parameters = {})
      begin
        @memcached.get(normalize(key, parameters)) && true
      rescue  Memcached::Stored
        true
      rescue Memcached::NotFound
        nil
      end
    end
def exists?(key, parameters = {})
      begin
        @memcached.get(normalize(key, parameters)) && true
      rescue  Memcached::Stored
        true
      rescue Memcached::NotFound
        nil
      end
    end
returns true/false/nil based on if data identified by the key & parameters
 is persisted in the store.

 With Memcached 1.2 protocol the only way to
 find if key exists in the cache is to read it.
 It is very fast and shouldn't be a concern.