$line =~ s/
    (
        (?:
            [^,]+
            ,
        ){3}
    )
    ([^,]+)
    (.*)
/   $2 > 310    ? "$1volemd$3"
  : $2 == 70    ? "$1volemd1$3"
  : "$1$2$3"
  ;
/exms;