Ternary search trees are interesting data structures that provide a means of storing and accessing strings. They combine the time efficiency of digital tries with the space efficiency of binary search trees. Unlike a hash, they also maintain information about relative order. I highly recommend the use of Test.pm, although, it is not required.
POD is readable with the 'perldoc' utility.
SEE ALSO Bentley, Jon and Sedgewick, Robert. Dr. Dobb's Journal, April 1998. Eighth Annual ACM-SIAM Symposium on Discrete Algorithms New Orleans, January, 1997.