title: How do I add two variables together and store the result into another variable?
body: <p>I can't figure out the most basic Tcl syntax, what is the right way to write the following:</p>
  
  <pre><code>set var1 5
  set var2 3
  set var3 $var1 - $var2; # error line
  
  puts $var3
  </code></pre>