title: Replacing regex with new regex
body: <p>Say I have </p>
  
  <p>"a acrobat jumped over an bridge"</p>
  
  <p>and I want to change this to</p>
  
  <p>"an acrobat jumped over a bridge".</p>
  
  <p>Right now, I'm using </p>
  
  <p><code>lyrics = re.sub(r" a (a|e|i|o|u|y){1}([a-z]+|[A-Z]+)", r" an (a|e|i|o|u|y){1}([a-z]+|[A-Z]+)", lyrics)</code></p>
  
  <p>and the resulting string doesn't replace in the way I'd hope it would, as expected. How else can I do this?</p>
  
  <p>To clarify, I want to be able to generalize this for every case, not just the example I used above.</p>