> New Notifiers: The central event handling engine in Tcl is now constructed on top of the system calls epoll or kqueue when they are available. The select based implementation also remains for platforms where they are not.

This is huge! A big portion of why concurrency in Tcl was so dated and why the language was considered so non-performant was because it relied on `select` despite `epoll` and `kqueue` being available for at least a decade.

Tcl is one of my favorite languages because of how easy it is to get started with and how easy metaprogramming is.