Well, Math::BigFloat is about floating point numbers. Not about integers. So, to me it makes a lot of sense to store it as a significant/exponent pair, and not a plain integer. Note that the internal representation is not "0E1". The internal representation is:

    {
        _e => 1,
        _es => '+',
        _m => [0],
        sign => '+',
    }
[download]

which corresponds to 0E1.