#include <iostream>
#include <iterator>
#include <regex>
 
int main()
{
   std::string html = "<ul><a href=\"http://stackoverflow.com\">SO</a></ul> "
                      "<ul>abc</ul>\n";
   std::regex url_re(R"(<ul>([\s\S]*?)<\/ul>)", std::regex::icase);
   std::copy( std::sregex_token_iterator(html.begin(), html.end(), url_re, 1),
              std::sregex_token_iterator(),
              std::ostream_iterator<std::string>(std::cout, "\n"));
}

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