title: What's the significance of `string is list` in Tcl
body: <p>As I understand in Tcl everything is list. so whats the significance of the 
  <code>string is list $var</code> check?</p>
  
  <p>So far only value of var I could make that check 0 is </p>
  
  <p><code>set var \\{</code> . </p>
  
  <p>For every other value of $var the check results into 1</p>