title: Forbidden characters in Groovy script filenames?
body: <p>I have written a tiny Groovy script (just a few simple instructions) and named it <code>a-b.groovy</code>.<br>
  My colleague has trouble running it and said:</p>
  
  <blockquote>
    <p>I believe '-' is illegal in Groovy scripts filenames</p>
  </blockquote>
  
  <p><strong>Question:</strong> What is the complete list of characters that are illegal in Groovy filenames?</p>
  
  <p><em>(Note: Unlike <a href="https://stackoverflow.com/questions/22135967/naming-convention-for-groovy-script-files">Naming convention for groovy script files</a>, my question is not about conventions)</em></p>