Error Unknown ref 'JSON::PP::Boolean'

Problem

When using JIRAPackage-5.0.3.opm, the OTRS logfile can show the following error message:

[Thu Jan  7 16:23:15 2016][Error][Kernel::System::Main::_Dump][1100] Unknown ref 'JSON::PP::Boolean'!
[Thu Jan  7 16:23:15 2016][Error][Kernel::System::Main::_Dump][1100] Unknown ref 'JSON::PP::Boolean'!

Solution

This error can be ignored since it does not have a negative impact.