5.6.1 is completely unsupported. It is dead. It is so entirely dead that if a security flaw allowing privilege escalation was uncovered, the most likely reponse from the Perl 5 Porters would be to recommend you upgrade. No one's really familiar with that codebase any more.

So I doubt anyone will bother fixing the regexp/closure issue — subsytems that have been heavily rewritten in the intervening years since the 5.6 line was released.