This is a just quick and short demonstration of my understanding of concurrency and conditional thread blocking utilizing the CondVar functionality in the rust programming language.
When you run the program it'll continuously read input through stdin. Enter 69 to have the word "hehe" written to the terminal. To exit to program, either enter 420 or just leave with CTRL-C.
When starting the program, before initiating any sort of input through stdin, an external thread is initialized which essentially does nothing, consuming no CPU time, until a certain variable is changed. While the thread is blocked, the main thread asks for the user to input shit. If the user inputs a 69 or 420 the variable is modified and then the external thread is notified of the modification of the shared variable. Upon notification, the external thread wakes and checks if the shared variable was modified to a particular value. If all goes well, the external thread completes its little sub-task and continues to loop, of course until a 420 is entered where it would then end itself.