title: I am having difficulties run Tcl script
body: <p>I have started learning TCL scripting language. I use ActivateState Tcl Devkit 5.3.0. 
  When I create new simulator it gives mistake like this:</p>
  
  <pre>
  invalid command name "new"
      while executing
  "new Simulator"
      invoked from within
  "set ns [new Simulator]"
  </pre>