To be fair,
BrowserUK certainly didn't claim that his regex processes XML, only that it does the job as reliably as the other possibilities. Since 'the job' was rather under-specified ("extract someresult from the following string …", which could of course be done by
perl -e 'print "someresult\n"'), I think it's difficult to say that
BrowserUK's solution doesn't (or does, for that matter) do it.