while ( reading from the input file yields a line of data ) {
   if ( the line begins with "RS," ) {
      replace the newline character(s) at the end of the line with a comma
      save this line in a variable called $line_out
   }
   elsif ( the line begins with "RAd," ) {
      replace the final newline character(s) with a comma (just like above)
      append this line to $line_out
   }
   elsif ( the line begins with "RC," ) {
      print $line_out with the current line appended to it.
   }
}