As with other Pseudo-Random Number Generator (PRNG) algorithms like the
Mersenne Twister (see Math::Random::MT), this algorithm is designed to
take some seed information and produce seemingly random results as output.

However, ISAAC (Indirection, Shift, Accumulate, Add, and Count) has
different goals than these commonly used algorithms. In particular, it's
really fast - on average, it requires only 18.75 machine cycles to generate
a 32-bit value. This makes it suitable for applications where a significant
amount of random data needs to be produced quickly, such solving using the
Monte Carlo method or for games.

WWW: http://search.cpan.org/dist/Math-Random-ISAAC-XS/