static boolean is_match(String r, String s) {
		// Case (2.) : starts with '^'.
		if (r.charAt(0) == '^') {
			return is_match_here(r.substring(1), s);
		}

		for (int i = 0; i <= s.length(); ++i) {
			if (is_match_here(r, s.substring(i))) {
				return true;
			}
		}
		return false;
	}