I dunno. It doesn't work for some reason:

open (OUT,  ">Curr_Closed.csv");
    open (RAW, "<Prelim_CC.csv") or die "ERROR: Could not open Curr_Cl
+osed.csv";
     while (<RAW>){
        chomp ($_);
        my @columns = split (/,/, $_, 10);
        $columns[9] =~ s/,/;/;
        print OUT $columns[9]."\n"}
    close (RAW);
    close (OUT);
[download]

What this does is takes only the first comma in 10th column and changes it to semilon. But fields that have more than one comma are still messed up.

Am I using regexp wrong?

Yes, you need g on the end

$columns9 =~ s/,/;/g;

Untested.

J.C.