title: Regular Expression to find string in Expect buffer
body: <p>I'm trying to find a regex that works to match a string of escape characters (an Expect response, see <a href="https://stackoverflow.com/questions/1988811/expect-get-variable-from-screen-region-based-on-row-and-column">this question</a>) and a six digit number (with alpha-numeric first character).</p>
  
  <p>Here's the whole string I need to identify: </p>
  
  <pre><code>\r\n\u001b[1;14HX76196
  </code></pre>
  
  <p>Ultimately I need to extract the string:</p>
  
  <pre><code>X76196 
  </code></pre>
  
  <p>Here's what I have already:</p>
  
  <pre><code>interact {
          #...
          #...
          #this expression does not identify the screen location
          #I need to find "\r\n\u001b[1;14H" AND "([a-zA-Z0-9]{1})[0-9]{5}$"
          #This regex was what I was using before.
          -nobuffer -re {^([a-zA-Z0-9]{1})?[0-9]{5}$} {
                  set number $interact_out(0,string)
          }   
  </code></pre>
  
  <p>I need to identify the escape characters to to verify that it is a field in that screen region.   So I need a regex that includes that first portion, but the backslashes are confusing me...</p>
  
  <p>Also once I have the full string in the $number variable, how do I isolate just the number in another variable in Tcl?</p>