For a long time, certain of Cisco's routers had the ability to run tcl scripts, particularily routers with voip loads, in order to perform credit card billings for voip connection validations. To me, the tcl scripting was a black art and not well documented.
That has changed. The capability has now become officially and publically supported. It is now known as the Cisco Embedded Event Manager. Part of it is integrated into SLA functionality. This, for example, provides the ability to adjust routing and other configuration details on the fly depending upon reachability testing. That one example barely covers the surface of what can be done to dynamically and automatically alter a router's functioning parameters.
That, in itself, is a two edged sword. But with today's interconnected, converged, flexible networks, sometimes one needs a trick like that to make things happen.
Some URL's:
