using xtags and io to modify foo.xml

[William C. Robertson]

After pulling and parsing an xml document, I would like to modify it and
save it again:
<%
File file=new File("/usr/local/foo.xml");
FileWriter fileWriter = new FileWriter( file );
%>
<io:pipe writer="<%= fileWriter %>">
        <xtags:copyOf select="//" />
</io:pipe>

Yet I get "Illegal to flush within a custom tag".  Does someone know why or
have an alternate solution?

Many thanks...