Every time I've tried building perl 5.17.x, 'make test' has failed because of t/op/fork.t (on RHEL) Patch mentioned in http://www.nntp.perl.org/group/perl.perl5.porters/2013/05/msg201627.html referring to https://rt.perl.org/rt3/Public/Bug/Display.html?id=117141 I'm not expecting this issue to be dealt with, but for a few years now, lib/Benchmark.t would occasionally fail for VMWare hosts, so I now patch it to change $delta from 0.4 -> 0.99