\startbuffer[test]
<something>
    <question>
        <tag name="whatever"><![CDATA[begin]]></tag>
        <content>something</content>
    </question>
</something>
\stopbuffer

\startxmlsetups xml:mysetups
    \xmlsetsetup{#1}{something}{xml:*}
\stopxmlsetups

\xmlregistersetup{xml:mysetups}

\startxmlsetups xml:something
    \xmlfilter{#1}{question/tag[@name=='whatever' and find(xml.tostring(text()),'begin')]/../command(xml:question:begin)}
\stopxmlsetups

\startxmlsetups xml:question:begin
    !!!!!!!!!!!!!!!!
\stopxmlsetups

\starttext
    test \xmlprocessbuffer{main}{test}{}
\stoptext
