title: How to match all X after Y?
body: <p>I have this string:</p>
  <pre><code>A1xB2xC3yD4xE5xF6x
  </code></pre>
  <p>I want to match (then replace) every <code>x</code>, but only the ones after <code>y</code>.  Expected matches: <code>x</code>, <code>x</code>, <code>x</code>.
  I tried this:</p>
  <pre><code>(?&lt;=y)x
  </code></pre>
  <p>But it doesn't work.  Supposedly it matches <code>x</code> preceded by <code>y</code>, but only IMMEDIATELY preceded by <code>y</code>.</p>
  <p>So I tried this:</p>
  <pre><code>(?&lt;=.*y.*)x
  </code></pre>
  <p>But apparently the <code>*</code> and even the <code>+</code> symbols are not valid and throw an error if used inside that group.</p>
  <p>Is there any way to do what I'm trying to do?</p>
  <p>The solution cannot be &quot;the last 3 <code>x</code>'s&quot;, because the number of <code>x</code>'s after <code>y</code> is unknown.</p>