+=head3 get_next_case ()
+
+Retrieves the next case from the reader.
+This method returns an array of scalars, each of which are the values of
+the data in the system file.
+The first call to C<get_next_case> after C<open> has been called retrieves
+the first case in the system file. Each subsequent call retrieves the next
+case. If there are no more cases to be read, the function returns an empty
+list.
+
+If the case contains system missing values, these values are set to the
+empty string.
+
+=head2 Miscellaneous subroutines
+
+The following subroutines provide (hopefully) useful information about the
+values retrieved from a reader.
+
+=head3 PSPP::format_value ($value, $variable)
+
+Returns a scalar containing a string representing C<value> formatted according
+to the print format of C<variable>.
+In the most common usage, C<value> should be a value of C<variable>.
+
+
+=head3 PSPP::value_is_missing ($value, $variable)
+
+Returns non-zero if C<value> is either system missing, or if it matches the
+user missing criteria for C<variable>.
+
+=cut