

          pipe [handle_var_r handle_var_w]
               Create a pipe.  If handle_var_r and handle_var_r are
               specified, then pipe will set the a variable named
               handle_var_r to contain the handle of the side of the
               pipe that was opened for reading, and handle_var_w will
               contain the handle of the side of the pipe that was
               opened for writing.

               If the handle variables are not specified, then a list
               containing the read and write handlew is returned as
               the result of the command.
