no XML rendered in this example, why not?

rubyonrails-talk
1

I know I'm calling the controller correctly, I get

XML Parsing Error: no element found <controller>.xml;example Line Number 1, Column 1:

def example     xml = Builder::XmlMarkup.new(:indent=>2)     xml.instruct!     xml.person     return xml

    respond_to do |format|       format.html # index.rhtml       format.xml { render :xml => xml }     end   end