Okay, I see your problem. You have potentially two records for each user - one containing a telephone number, and the other a fax number, yes?

This means that you really can't print each line as you iterate, because you need to gather both numbers. One approach to this problem may be to use a hash. Something like the following may work:

my %users;
while (<CSV>) {
    next if ($. == 1);
    if ($csv->parse($_)) {
        my @columns = $csv->fields();
        my @choppedcols = $csv->fields();
        
        my $username =  lc($columns[1]);
        $users{$username}{first_name} = ($columns[2]); 
        $users{$username{last_name} = ($columns[3]);
        # etc... then
        my $telephone = ($columns[8]).-($columns[6]);
        if ($columns[8] == 1) {
            $users{$username}{fax_number} = $telephone;
        }
        else {
            $users{$username}{phone_number} = $telephone;
        }
    }
}
[download]

And then...

for my $user (keys %users) {
    print "dn: uid=$user\n",
        "givenName: $users{$user}{first_name}\n",
        "sn: $user{$user}{last_name}\n",
        #etc...
        "telephonNumber: $users{$user}{phone_number}\n",
        "faxNumber: $users{$user}{fax_number}\n";
}
[download]

Cheers,
Darren :)