...
    if ( $sum > 310 ) {
        my $sum2 = "volemd";
        #chomp($sum2);  not needed
        $line =~ s/(.*?)\,(.*?)\,(.*?)\,(.*?)\,(.*?)\,(.*?)/$1\,$2\,$3\,$sum2,$5,$6/g;
    }
    elsif ( $sum == 70 ) {
        my $sum3 = "volemd1";
        #chomp($sum3);  not needed
        $line =~ s/(.*?)\,(.*?)\,(.*?)\,(.*?)\,(.*?)\,(.*?)/$1\,$2\,$3\,$sum3,$5,$6/g;
    }
 ...

##</code><code>##

623192729079,510993192729079,19,volemd,0,133,282051608,
623192728769,510993192728769,19,310,0,118,84950715,
623192729901,510993192729901,19,volemd1,0,
623192609007,510993192609007,19,22,0,
623416771429,510993416771429,19,volemd1,0,
622319309157,510992319309157,19,22,0,
623192724581,510993192724581,19,volemd1,0,
622319381619,510992319381619,19,volemd1,0,
622198575655,510992198575655,19,1,0,
623192724589,510993192724589,19,volemd1,0,
622743581281,510992743581281,19,71,0,