title: Regex that matches valid Ruby local variable names
body: <p>Does anyone know the rules for valid Ruby variable names? Can it be matched using a RegEx?</p>
  
  <p><strong>UPDATE:</strong> This is what I could come up with so far:</p>
  
  <pre><code>^[_a-z][a-zA-Z0-9_]+$
  </code></pre>
  
  <p>Does this seem right?</p>