Math::Calc::Units is a Perl module and associated
command-line tool 'ucalc' that performs simple
calculations while taking the units used into
consideration, and automatically determines a
reasonable set of units for the output. For
example, 384Kbps will be described as 48KB/sec and
3.955 GB/day. 20MB/384Kbps will produce "7 minute
6 sec".