Tcl is part of Cisco’s IOS router operating system, and as such is included in all high-end Cisco routers and switches. Tcl 8.3.4 was introduced in Cisco IOS 12.3(2)T.4. The newest versions of Salvatore Sanfilippo’s Hping rely on Tcl, which he says “will likely merge with Hping” TCL’ing Your Cisco Router by Peter J. Welcher shows some of what can be done with Tcl on the router.”]
Source: https://taosecurity.blogspot.com/2005/03/cisco-routers-run-tcl-this-morning-i.html