Completely untested, but I'd start with something like this:

while (<infile>) {
  my @line = split /,/, $_;
  [case code here for determining what data you need]
  open(FH,">$_[1].txt");
  print FH [data you need in said file]
  }
[download]

If your file names are predetermined by some other method, set up a hash with 1-24 as your keys, and use them in the open statement.