title: Regex Optional Quotation Marks
body: <p>I need a regex to detect the character 'a', followed by a space, followed by a word, or words encapsulated in quotation marks. I need to take this word or words, and use them in a substitution, like "b \1"</p>
  
  <p>So:</p>
  
  <pre><code>a "foo bar"
  a 'foo bar'
  a foo
  a 
  a foo bar
  </code></pre>
  
  <p>should become:</p>
  
  <pre><code>b foo bar
  b foo bar
  b foo
  a 
  a foo
  </code></pre>
  
  <p>What is the regex I need?</p>