title: regex for replacing with tab
body: <p>I am having a large data base around 80k data.
  There is customer reference number followed by customer name. The problem is customer
  reference number may have alphabets, special characters and so on. But the characters will be in upper case letter only and it will not be more than two characters and never lowercase 
  letters.</p>
  
  <p>So, I'm trying to use regular expression to search a uppercase followed by two lowercase 
  letters.</p>
  
  <p>I succeeded in doing so, by using the expression</p>
  
  <pre><code>(.)[(A-Z)][(a-z)][(a-z)]
  </code></pre>
  
  <p>But I don't know how to give tab, as replacing it with <code>\t \1</code> deletes the first three 
  character. Please help. and also please explain me, how it works.</p>