title: Sed: Regex doesn't match and I have no idea why
body: <p>I have a long list of commands (most of them sed) piped together, the sed where my problem is gets input that looks like this:</p>
  
  <pre><code>v5.3-rc4/
  v4.9.123/
  </code></pre>
  
  <p>and it should turn them into something like this:</p>
  
  <pre><code>v5.03-rc4/
  v4.09.123/
  </code></pre>
  
  <p>My current attempt looks like this:</p>
  
  <pre><code>sed 's/v\([0-9]*\)\.\([0-9]\)\((\.[0-9]*)?(-rc[0-9]*)?\)\//v\1.0\2\3\//g'
  </code></pre>
  
  <p>I have already double-checked this in a RegEx-debugger and it seems to be correct. Can anyone tell me, what's wrong with this?</p>