title: Regex pattern to handle both case-sensitive and case-insensitive in a single statement
body: <p>I have a small regex to handle. I have 2 different terms. </p>
  
  <ol>
  <li>"United States", which I would like to match ignoring the case</li>
  <li>"US", which I would like to match <em>without</em> ignoring case.</li>
  </ol>
  
  <p>I want to do the following two regex substitution in a single regex substitute statement.</p>
  
  <pre><code>clntxt = re.sub('(?i)United States', 'USA', "united states")
  # Output: USA
  clntxt = re.sub('US', 'USA', "US and us")
  # output: USA and us
  </code></pre>
  
  <p>I need something like </p>
  
  <pre><code>clntxt = re.sub('(?i)United States|(?s)US', 'USA', "united states and US and us")
  # output: USA and USA and us
  </code></pre>
  
  <p>How can I achieve the above?</p>