MPI a very powerful tool that allows one to use relatively simple programming to add things to descriptions, store and recall bits of information, and a variety of other effects. It can have a lot of useful applications, but it isn't exactly easy to get into. These resources are designed to provide simple examples and samples that should allow anyone to harness some of the tricks MPI permits.
Entry: lrand and you, or how to pull a random string from a list.
Entry: dice, and the fine art of randomized numbers.
A complete manual of available mpi commands is available at the MPI Reference Manual.