This man page seems to contradict itself, but perhaps it's not optional, as mentioned below. 

MAIN VARIABLES

     All ports are required to set certain variables.

     name

         Full name of port.

         Type: required

         Example:

               name XFree86

     version

         Upstream version of software.

         Type: required

         Example:

               version 4.2.1

     epoch

         If a port's version numbering changes such that a newer version looks

         older than the previous version, the epoch should be increased. Often

         the epoch is formatted like a date.

         Type: optional

         Default: 0

         Example:

               epoch 20041231

     description

         One line description of the software and what it does.

         Type: required

         Example:

               description Dictionary Server Protocol (RFC2229) client

     long_description

         A verbose description of the software and what it does.

         Type: required

         Example:

               long_description The GNU Image Manipulation Program \

                   (GIMP) is a powerful tool for the preparation and \

                   manipulation of digital images. The GIMP provides \

                   the user with a wide variety of image manipulation, \

                   painting, processing, and rendering tools.

     revision

         Local revision number of Portfile.  Increment for port revisions

         which would change its installation in any way.

         Type: optional

         Default: 0

--

Paul Beard

words: http://paulbeard.org/wordpress

pictures: http://www.flickr.com/photos/pdb206/

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