I'm trying to loop among some strings delimited by a '$' pair in a line, replacing each match with a specific value in order to get an output line with all markers replaced but I'm stuck at the second match as I don't know how to concatenate the new replacement value:

```
const boost::regex expression( "\\$[\\w]+\\$" );
string fileLine( "Mr $SURNAME$ from $LOCATION$" );
string outLine;

string::const_iterator begin = fileLine.begin();
string::const_iterator end = fileLine.end();

boost::match_results<string::const_iterator> what;
boost::match_flag_type flags = boost::match_default;

while ( regex_search( begin, end, what, expression, flags ) ) {
  actualValue = valuesMap[what[0]];

  ostringstream t( ios::out | ios::binary );
  ostream_iterator<char, char> oi( t );

  boost::regex_replace( oi, begin, end, expression, actualValue, 
                        boost::match_default | boost::format_first_only );
  outLine.append( t.str() );
  begin = what[0].second;
}

```

The problem is in the outLine.append( t.str() ) as the concatenation is not done properly because after the first match, the outLine holds already some of the characters preceding the next match.