The Cont module provides methods for working with continuations. Continuations are a way to save the execution state of a program so that it can be resumed later. They are used for advanced control flow structures such as coroutines, generators, and so on. Ruby have a built-in support for continuations, but it is deprecated and should not be used. This implementation uses the 'fiber' library based on https://github.com/minoki/delimited-continuations-in-lua . That library is released under the MIT license. Caution: The continuations of this implementation are 'one-shot', So they can only be resumed once. If you try to resume a dead continuation, an exception will be raised.