title: Extracting a pattern from a string?
body: <p>Ok so say I have a word: <code>BEER</code></p>
  
  <p>I want to create a string like this: <code>- E E -</code></p>
  
  <p>See that all letters other than the <code>E</code> have been replaced with a <code>-</code> and a space been introduced between each character. I can do the latter pretty easily, not the former.</p>
  
  <p>Also, it may be of help that the character not to be blanked out is not known. I have to make that decision based on a <code>Set</code> of characters. </p>
  
  <p>So, if I have a <code>Set</code> of words: <code>BEER HERE HAIR</code>, and I want <code>E</code> not to be blanked, my output should be this: <code>- E E -</code> <code>-E - E</code> <code>- - - -</code>.</p>
  
  <p>How should I do this?</p>