Don't use get_xpath, use findnodes, as the docs state:
XML::Twig does not provide natively full XPATH support, but you can use "XML::Twig::XPath" to get "findnodes" to use "XML::XPath" as the XPath engine,
with full coverage of the spec.
Actually the development version of XML::Twig produces the following message in that situation:
error in xpath expression //OverallConnectionPoolStatus/FlowRater/Name/text() around text()
the expression is a valid XPath statement, and you are using XML::Twig::XPath, but
you are using either 'find_nodes' or 'get_xpath' where the method you likely wanted
to use is 'findnodes', which is the only one that uses the full XPath engine