title: Regex to match abc OR a OR c
body: <p>Say I am considering patters which are matched by regexes <code>A</code> and <code>C</code>.  I am searching for patterns which match either <code>A</code> or <code>C</code> alone, OR <code>A</code> joined to <code>C</code> by some joining pattern <code>B</code>, i.e. <code>ABC</code>.</p>
  <p>I could almost do <code>[AC(ABC)]</code>, but I would like to be able to name groups <code>A</code> and <code>C</code> and extract them once matched which would give an error here since I can't have multiple groups with the same name.</p>
  <p>EDIT:</p>
  <p>Since it seems people are getting confused, here is an example with my current scenario.  I am looking for numbers which may be expressed as mixed fractions, i.e. <code>1 1/2</code>.  However I need to be able to match either <code>1 1/2</code>, <code>1</code> or <code>1/2</code>.  This would correspond to <code>A = &quot;\d+&quot;</code>, <code>B=&quot; &quot;</code> and <code>C=&quot;\d+/\d+&quot;</code>.</p>
  <p>Note that this is a simplified case of my actual application, due to massive amounts of inconsistencies in the data I'm parsing, the actual regexes for A, B and C that I'm dealing with are quite a bit more complex.</p>