std::regex_iterator<BidirIt,CharT,Traits>::operator*,operator->

From cppreference.com
const value_type& operator*() const;
(1) (since C++11)
const value_type* operator->() const;
(2) (since C++11)

Extracts the current std::match_results from a regex_iterator:

Return value

1) Returns a reference to the current std::match_results.
2) Returns a pointer to the current std::match_results.

Example

#include <iostream>
#include <string>
#include <regex>
 
int main()
{
    std::regex expression("[1234]");
    std::string searchStr("1.1a2b3cjk34");
 
    for (std::regex_iterator<std::string::iterator> it{
        searchStr.begin(), searchStr.end(), expression
    }, last{}; it != last; ++it) {
        std::cout << it->str();
    }
}

Output:

112334