title: how the upvar command works in TCL?
body: <p>I have a question about upvar command in TCL. Using upvar command, we have have a reference to a global variable or a local variable in other procedure. I saw the following code:</p>
  
  <pre><code>proc tamp {name1 name2} {
      upvar $name1 Ronalod
      upvar $name2 Dom 
      set $Dom "Dom"
  }
  </code></pre>
  
  <p>this procedure is called as <code>tamp name1 name2</code> , and there is no global variables name1, name2 defined outside of it, how this upvar works in this case?</p>