docs: protected List<String> extractWords() throws IOException
      {
          while( true ) {
              lineNumber++;
              String line = in.readLine();
              if( line == null ) {
                  return null;
              }
  
              // skip comment lines
              if( hasComment ) {
                  if( line.charAt(0) == comment )
                      continue;
              }
  
              // extract the words, which are the variables encoded
              return parseWords(line);
          }
      }