Can't get your code to work. It dies with message:

Operation `**': no method found,
        left argument in overloaded package Math::BigFloat,
        right argument has no overloaded magic at test.pl line 17.
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Update:

BTW It seems that using Math::BigFloat methods directly is slighly faster then relying on overloaded operations:

use Benchmark;
use Math::BigFloat;

timethese(1000, {
    Methods => sub { Math::BigFloat->new(100)->fmul(Math::BigFloat->ne
+w(100)) },
    Operations => sub { Math::BigFloat->new(100) * Math::BigFloat->new
+(100) },
});



bash-2.05a$ perl test.pl
Benchmark: timing 1000 iterations of Methods, Operations...
   Methods:  2 wallclock secs ( 1.48 usr +  0.01 sys =  1.49 CPU) @ 67
+1.14/s (n=1000)
Operations:  1 wallclock secs ( 1.63 usr +  0.00 sys =  1.63 CPU) @ 61
+3.50/s (n=1000)
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--
Ilya Martynov (http://martynov.org/)