Actually, I just did this to fix it following an earlier suggestion

$id = 1
open(MYFILE,"/var/tmp/mylist.dat") or die "Cant open mylist.dat"

while (<MYFILE>) {
      chomp;
      split/,/;
      die "Request Id $id already present in file\n" if $_[0] eq $id;
                }

close MYFILE;
[download]