Please see attached files Reproducible: Always
Created attachment 403834 [details] emerge --info output
Created attachment 403836 [details] /var/tmp/portage/dev-perl/XML-NamespaceSupport-1.110.0-r1/temp/build.log
Sorry but I can't reproduce this error. JSON/PP.pm is the culprit in your case (malformed for some reason) and is part of the dev-lang/perl-5.20.2 package. Please reinstall the latter and let us know. Thank you.
Attaching the content of /usr/lib/perl5/5.20.2/JSON/PP.pm also seems useful, because that is clearly a syntax error in JSON/PP.pm itself, and I would expect any code that uses it to fatal. eg: Please try replication of the fault by doing: perl -MJSON::PP -e1 If that fails, we know the file is corrupted. If it doesn't fail, we need to work out why XML-NamespaceSupport changes perl so that loading breaks.
Also, did you ever user GCC 5 ?