title: Having issue with back reference in TCL
body: <p>I have the following code:</p>
  
  <pre><code>set a "10.20.30.40"
  regsub -all {.([0-9]+).([0-9]+).} $a {\2 \1} b
  </code></pre>
  
  <p>I am trying to grep 2nd and 3rd octet of the IP address. </p>
  
  <p>Expected output:</p>
  
  <pre><code>20 30
  </code></pre>
  
  <p>Actual output:</p>
  
  <pre><code>20 04 0
  </code></pre>
  
  <p>What is my mistake here?</p>