Update

Miss some info, I actually tested before reply.

• The version of BigFloat coming with my perl (5.8.0) is version 1.35, which has the same problem bart described.
• I downloaded 1.40, it worked as Roger described.
• A reasonable guess is that at the time Roger download Perl, it had already been rebundled with bunch of fixes, including some fixes to BigFloat.
• Chatted with Roger, he confirmed he used 1.38, which is higher than my 1.35.

Original

Both bart and Roger are right, as they used different versions of Math::BigFloat.

Just go to CPAN, get the latest version, which I believe is 1.40, and your problem will go away.