Math::Decimal64 supports up to 16 decimal digits of significand
(mantissa) and an exponent range of -383 to +384.
The smallest expressable value is -9.999999999999999e384 (which
is also equivalent to -9999999999999999e369).
The largest expressable value is 9.999999999999999e384 (which
also equivalent to 9999999999999999e369).
The closest we can get to zero is (plus or minus) 1e-384
(which is also equivalent to 1000000000000000e-399).

This module allows decimal floating point arithmetic via
operator overloading - see "OVERLOADING".

In the documentation that follows, "$mantissa" is a perl scalar
holding a string of up to 16 decimal digits, optionally prefixed
with a '+' or '-' sign:
$mantissa = '1234';
$mantissa = '1234567890123456';