Not that it's of great importance, but is there a reason that you've chosen to use "%.100f" formatting instead of "%.100g" formatting ?
The "%.100g" formatting should remove any trailing zeros, thereby alleviating the need for the regex.

I know that, on some systems, %g formatting can be buggy, but I don't know of any system where "%.100g" misbehaves && "%.100f" functions correctly.

Cheers,
Rob