+ /* Here, we have a single value. If 'range' is set, it is the ending
+ * of a range--check its validity. Later, we will handle each
+ * individual code point in the range. If 'range' isn't set, this
+ * could be the beginning of a range, so check for that by looking
+ * ahead to see if the next character to be processed is the range
+ * indicator--the minus sign */
+