It's more like "eval" in the stack frame you select. This added to the fact Tcl, like Lisp, has the same form for all the commands, allow to do anything you cou

It's more like "eval" in the stack frame you select. This added to the fact Tcl, like Lisp, has the same form for all the commands, allow to do anything you could conceive and it will look like if it's part of the language. For instance you can do a looping construct that works in a different way depending on the calling function name or state or any other crazy stuff like that.