From README:
    This module implements a least recently used (LRU) cache in memory
    through a tie interface. Any time data is stored in the tied hash, that
    key/value pair has an entry time associated with it, and as the cache
    fills up, those members of the cache that are the oldest are removed to
    make room for new entries.

    So, the cache only "remembers" the last written entries, up to the size
    of the cache. This can be especially useful if you access great amounts
    of data, but only access a minority of the data a majority of the time.

    The implementation is a hash, for quick lookups, overlaying a doubly
    linked list for quick insertion and deletion. On a WinNT PII 300, writes
    to the hash were done at a rate 3100 per second, and reads from the hash
    at 6300 per second. Work has been done to optimize refreshing cache
    entries that are frequently read from, code like $cache{entry}, which
    moves the entry to the end of the linked list internally.

WWW: http://search.cpan.org/dist/Tie-Cache/

-- Alex Kapranoff <kapr@crosswinds.net>