title: Can someone explain me what is the meaning of all the code inside these parentheses: RegexpTokenizer(r'\w+|$[0-9]+|\S+')?
body: <p>I've been reading a book about NLP recently and in one part the author show me how to tokenize a piece of text. </p>
  
  <p>And then he show me this code:</p>
  
  <pre class="lang-py prettyprint-override"><code>sent0 = """Thomas Jefferson began building Monticello at the age of 26."""
  tokenizer = RegexpTokenizer(r'\w+|$[0-9]+|\S+')
  print(tokenizer.tokenize(sent0))
  </code></pre>
  
  <p>What I don't understand is the meaning of this "r'\w+|$[0-9]+|\S+'". Can someone explain me just that?</p>