The SHA module allows you to use the NIST SHA message digest algorithm
from within Perl programs.

The final message digest value is returned by the digest operation as
a 20-byte binary string. This operation delivers the result of
operations since the last new or reset operation. Once the operation
has been performed, the context must be reset before being used to
calculate another digest value.

WWW: http://search.cpan.org/dist/SHA/