title: Get substring between first occurance of "A" and last occurance of "B"
body: <p>I have a string which has two tokens that bound a substring that I want to extract, but the substring may contain the tokens themselves, so I want between the 1st occurrence of token A and the last occurrence of token B.  I also need to search for the tokens in a case-insensitive search.</p>
  
  <p>Tried to wrap my head around using regex to get this, but can't seem to figure it out.  Not sure the best approach here.  String.split won't work.  </p>
  
  <p>I can't modify the casing of the data between the tokens in the string.</p>