Handlers are used to simulate backtracking in a searching algorithm.
Handlers are used to simulate concurrency.
Continuation is wrapped and is executed outside of the original handler.
Captured continuations are resumed multiple times.
Captured continuations are resumed at most once.
Captured continuations are resumed exactly once.
Resumed continuations form a deep stack (continuations are resumed in a non-tail position).
Handlers form a deep stack (might be dynamically interleaved).