Tcl is great as an extension language for applications. There are several reasons for this. The most obvious one is the syntax. A Tcl function call looks how a

Tcl is great as an extension language for applications. There are several reasons for this. The most obvious one is the syntax. A Tcl function call looks how a normal command typed on the shell would look like. You quote variables, not values. So any Tcl function can invoked by the user as easily as you would have in a command interpreter. Consequently, Tcl is used in many applications for command input/scripting. Especially in chip design, which Tcl was created for (Tool Control Language). Tcl is also easy to link into your executable. Finally, and RMS won't like that, Tcl being BSD-licensed means, that there are no challenging license terms for including it in closed-source projects, as most commercial applications.