+=head2 update
+
+Automatically update the progress bar based on the position of the
+filehandle given at construction time.
+
+=over
+
+=item ARGUMENTS
+
+=over
+
+=item so_far
+
+Current progress point; this defaults to the current position of the
+filehandle. [You probably don't actually want to ever give this.]
+
+=back
+
+=back
+
+=cut
+