TCL versions of the example programs in David Beazley's Python talk A Curious Course On Coroutines And Concurrency, and notes to go along with his slides on how TCL coroutines differ from Python coroutines.
tcl 8.6 for coroutines, tcllib for the generator and coroutine packages, and tDOM for XML parsing. If your OS's tcl distribution splits threads into a separate package (Like Ubuntu), you'll want that too.