The String::CRC::Cksum module calculates a 32 bit CRC, generating the same
CRC value as the POSIX cksum program. If called in a list context, returns
the length of the data object as well, which is useful for fully emulating
the cksum program. The returned checksum will always be a non-negative
integral number in the range 0..2^32-1.

Despite its name, this module is able to compute the checksum of files as
well as of strings. Just pass in a reference to a filehandle, or a
reference to any object that can respond to a read() call and eventually
return 0 at "end of file".

Beware: consider proper use of binmode() if you are on a non-UNIX platform
or processing files derived from other platforms.