Simulation of http://en.wikipedia.org/wiki/Two_envelopes_problem
This is mostly a vehicle for writing simple programs in many different languages, getting them to execute, and comparing implementations.
This problem is a bit more involved than "Hello World" as it uses branching, looping, randomness, functions, and printing.
More detailed cross-language programs in fewer languages can be found at https://github.com/dfings/project-euler.