boost::regex extract search term

Question

How to extract a search term using boost::regex in C++ , especially when the term has html entities in it.

Eg

p=test&test&sort=price
Search Term would be 'test&test'

p=test&test&sort=price
Search Term would be 'test&test'

Boost Regex code is as follows

bool regexExtract(const string &strInput,string &strOutput,const string& regex)
{
  bool succ = false;
  if ( ! strOutput.empty() )
  {
    boost::regex re(regex, boost::regex::perl);//,boost::regex::perl | boost:regex::icase);
    boost::sregex_iterator res(strInput.begin(),strInput.end(),re);
    boost::sregex_iterator end;
    for (; res != end; ++res)
        cout << (*res)[0] << std::endl;
  }
  return succ;
}

with regex string re = "p=(([^&;#]|(&.*?;))*).*"; it prints below

p=test&test&sort=asc

while same regex in perl works perfectly fine

echo "p=test&asd;test&sort=asc" | perl -ne 'if ( $_ =~ /p=(([^\&;#]|(&.*?;))*).*/){print $1;}'
test&asd;test