prove -v -l t/14_serializer/02_request_json.t
ok 1 - response content looks good for PUT / HASH(0x2249dc8)
This is the devel branch on Perl 5.14.2.
Have you seen any other instance of that hanging since the creation of the issue?
I tried 5.14.2 on my machine, and it works. There have been no other reports of problems with 5.14.2, so I'll flag this as a one-off and close the issue.