freebsd-ports/security/p5-MD5/pkg-descr

The MD5 module allows you to use the RSA Data Security
Inc. MD5 Message Digest algorithm from within Perl
programs.

A new MD5 context object is created with the new
operation.  Multiple simultaneous digest contexts can be
maintained, if desired.  The context is updated with the
add operation which adds the strings contained in the LIST
parameter. Note, however, that add('foo', 'bar'),
add('foo') followed by add('bar') and add('foobar') should
all give the same result.                        

The final message digest value is returned by the digest
operation as a 16-byte binary string. This operation
delivers the result of add operations since the last new
or reset operation. Note that the digest operation is
effectively a destructive, read-once operation. Once it
has been performed, the context must be reset before being
used to calculate another digest value.

Several convenience functions are also provided. The
addfile operation takes an open file-handle and reads it
until end-of file in 1024 byte blocks adding the contents
to the context. The file-handle can either be specified by
name or passed as a type-glob reference, as shown in the
examples below. The hexdigest operation calls digest and
returns the result as a printable string of hexdecimal
digits. This is exactly the same operation as performed by
the unpack operation in the examples below.

The hash operation can act as either a static member
function (ie you invoke it on the MD5 class as in the
synopsis above) or as a normal virtual function. In both        
cases it performs the complete MD5 cycle (reset, add,
digest) on the supplied scalar value. This is convenient
for handling small quantities of data. When invoked on the
class a temporary context is created. When invoked through
an already created context object, this context is used.
The latter form is slightly more efficient. The hexhash
operation is analogous to hexdigest.