* Verify current '_' is ok, then move on to next character,
	 * otherwise follow through on to error.
	 */
	if (c == '_' && !(flags & TCL_PARSE_NO_UNDERSCORE)) {
	    const char *before, *after;

	    if (p==bytes) {
		/* Not allowed at beginning  */
		goto endgame;
	    }
	    /*
	     * span multiple numeric whitespace
	     *              V
	     *   example: 5___6
	     */