Significant figures is not equivalent to the number of decimal places - This however is a fairly common mistake to make. The thread link provided by broquaint is quite informative as to the role and calculation of significant figures, in particular, this post from davis, which points to the Math::SigFigs module on CPAN.

 

perl -le 'print+unpack("N",pack("B32","00000000000000000000001001010001"))'