void tokenize(String pat) throws javax.xml.transform.TransformerException
  {
    tokenize(pat, null);
  }
void tokenize ( String pat ) throws javax . xml . transform . TransformerException { tokenize ( pat , null ) ; }
Walk through the expression and build a token queue, and a map of the top-level
elements.
@param pat XSLT Expression.

@throws javax.xml.transform.TransformerException