Tcl stands for "tool command language" and is pronounced "tickle." It is actually two things: a language and a library.
First, Tcl is a simple textual language, intended primarily for issuing commands to interactive programs such as text editors, debuggers, illustrators, and shells. It has a simple syntax and is also programmable, so Tcl users can write command procedures to provide more powerful commands than those in the built-in set.
Second, Tcl is a library package that can be embedded in application programs.
Integrated development environments and other tools to help Tcl/Tk developers.
All the software available via the links in this category is written in Tcl/Tk.
XOTcl (pronounced exotickle) is an object-oriented scripting language based on MIT's OTcl.