

          pipe [handle_var_r handle_var_w]
               Create a pipe (see the pipe system call manual page).
               If handle_var_r and handle_var_r are specified, then
               variable handle_var_r will contain the handle opened
               for reading and handle_var_w will contain the handle
               opened for writing.  If the handle variables are not
               specified, then a list containing the read followed by
               the write handle is returned as the result of the
               command.
