In the POD of new in TAP::Harness there is
lib => [ 'lib', 'blib/lib' ],
which should be
lib => [ 'lib', 'blib/lib', 'blib/arch' ],
which was pointed out to me by Eric Wilhelm. I ran into this issue
because some of the tests of Math::GSL were failing only when run under
TAP::Harness with the first set of lib directories.
Thanks for maintaining TAP::Harness!