setjmp and longjmp allow a program to save an execution context and return to it at a later point in time, it is used to implement complicated flow control within programs, such as threads.

Write an EXAMPLES section for the setjmp(3)/longjmp(3) manpage(s) showing the usage of the functions defined in those manpage(s) in a plausible, real-world and if possible only semi-contrived scenario.

All examples should follow the style guidelines in the style(9) manpage.

All examples should be written in a manner that is self-documenting and make copious use of comments in order to explain the actions being taken.

Examples should be real and working code. They should not include headers or even a main function, but it should be reasonable for a developer to copy and paste an example from a manpage and expect it to work.

An example of a manpage with excellent example code is umtx(2).

Deliverables: A complete EXAMPLES manpage section in mdoc format.