title: regex - add dot prefix excluding words that already have a dot
body: <p>Lets say I have the following input strings:</p>
  
  <pre><code>range (bar | thumb_1 | thumb_2 | fill)
  range(bar|thumb_1|thumb_2|fill)
  .root.range.bar
  </code></pre>
  
  <p>Then I want the following output:</p>
  
  <pre><code>.range (.bar | .thumb_1 | .thumb_2 | .fill)
  .range(.bar|.thumb_1|.thumb_2|.fill)
  .root.range.bar
  </code></pre>
  
  <p>So far I have this:</p>
  
  <pre><code>void setup() {
    test("range (bar | thumb_1 | thumb_2 | fill)");
    test("range(bar|thumb_1|thumb_2|fill)");
    test(".root.range.bar");
  }
  
  void test(String in) {
    String r  = in.replaceAll("(\\w+)", "\\.$1"); // add . prefix to every word 
    println(r);
  }
  </code></pre>
  
  <p>The problem is that if the word already has a dot prefix it will add another one.
  I have been trying all kinds of things with <code>[^\\.]</code>.
  But either it does not working on the last input string, or it starts eating wrong characters on the first and second input string.</p>
  
  <p>How can I correctly ignore the cases where there is already a dot in front?</p>