I note you're running blead (5.11.0). The problem there might lie with something other than Math::Pari (eg Test::Harness).

Do you have a perl-5.10.0 to try it out on ? From where does one obtain the perl-5.11.0 source ? (I can't find it anywhere, though quite a few people seem to have located it ... I'll keep looking for it.)

Cheers,
Rob