Just to give a sign of life. I have looked into this. As with many other bugs in the Math::Big(Int|Float|Rat) modules, this bug is related to the broken OO-implementation in these modules. I am working on a patch for Math::BigInt which will fix this.
Fri Nov 25 14:19:18 2016peter.john.acklam [...] gmail.com - Status changed from 'open' to 'resolved'
Fri Nov 25 14:19:18 2016peter.john.acklam [...] gmail.com - Fixed in 0.15 added