The Tcl (Tool Command Language) language is a powerful scripting language with C-like syntax that supports TCP/IP networking, event-driven I/O, and other traditional programming constructs. The Tk Windowing Toolkit enables creation of sophisticated Windows programs with a few lines of Tcl code. This version of Tcl includes a bytecode compiler, safe-Tcl enhancements, and binary data support.
Tcl/Tk 8.3.4 focuses mainly on stability and build fixes. Changes and bug fixes are detailed here. Tcl/Tk is covered under an open source, free, BSD-style license.