title: regular expression to match any comma separated value
body: <p>I'm trying to send a regex to a mongo db that will match a comma separated value. </p>
  
  <p>For example 'aaa' should match:</p>
  
  <pre><code>aaa, ancient, pattern, discipleship, faithful, followers         matches
  lowers,aaa, gospel, righteousness, strengthen, family       matches
  lowers, aaa , gospel, righteousness, strengthen, family     matches
  lowers, goaaaspel, righteousness, strengthen, family        no match
  lowers, aaaspel, righteousness, strengthen, family          no match
  lowers, gospel aaa truth, righteousness, strengthen         no match
  lowers, gospel aaa, righteousness, strengthen, family       no match
  lowers, gospel, righteousness, strengthen, family aaa        no match
  lowers, gospel, righteousness, strengthen, family, aaa       matches
  </code></pre>
  
  <p>Thanks.</p>