This memory leak (I assume that it's the same %+ leak unless there were two different leaks associated with %+) affected me writing Date::Manip so I've been tracking it fairly closely. The leak exists in:

   5.10.1
   5.12.4
   5.14.2
   5.15.5

The bug has been fixed in:

   5.15.6

So unfortunately (to my knowledge) there is currently no released stable version which does not suffer from the leak, and unless they release a maintenance version of 5.14, it won't be until fixed in a stable release until 5.16.