You need to brush up on your xpath, the element node you're selecting ( ClinVarAccession with an @Acc attribute ) has no children or content -- it has no value

If you want the value of the @Acc attribute do like tangent shows in Re: Using findvalue in XML::Twig::XPath, select the attribute

In reply to Re: Using findvalue in XML::Twig::XPath ( xpath is xpath ) by Anonymous Monk
in thread Using findvalue in XML::Twig::XPath by jswamin

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