Tentative fix for #227. (#230)

Fixes #227.

test/issue227.cpp

@@ -0,0 +1,19 @@
+/*
+* Copyright (c) 2024
+* Christian Mazakas
+*
+* Use, modification and distribution are subject to the
+* Boost Software License, Version 1.0. (See accompanying file
+* LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+*
+*/
+
+#include <boost/regex.hpp>
+#include <string>
+
+int main() {
+   boost::regex rx("(*ACCEPT)*+\\1((*ACCEPT)*+\\K)");
+   std::string str = "Z";
+   boost::smatch what;
+   boost::regex_search(str, what, rx, boost::match_default | boost::match_partial);
+}