Perl extension for calculating cksum-compatible checksums

 String::CRC::Cksum 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.