title: TCL use "eq" or "==" when the argument can be a list or a string
body: <p>I have the following if loop:</p>
  
  <pre><code>if { expr { $Node_3 eq "BadAngle" } } {
    return "BadAngle"
  }
  </code></pre>
  
  <p>Node_3 can be a list containing coordinates, or the simple string "BadAngle"
  I use TCLPro 1.4 for debugging and TCL 8.6. I get:</p>
  
  <p>*<strong>syntax error in expression " expr { $Node_3 eq "BadAngle" } "*</strong></p>
  
  <p>I then also tried:</p>
  
  <pre><code>if { [ expr { $Node_3 eq "BadAngle" ] == 1 } } {
     return "BadAngle"
  }
  </code></pre>
  
  <p>But i get the same error.
  Also: What is the better alternative in this case: To use "==" or "eq", I think "eq" because a list is a kind of a string..or?</p>