while (<FILE>) {
  if (/,/) {
    process_data(@data);
    @data = split /,/, $_;
  } else {
    $data[$#data] .= $_;
  }
}
[download]

Not tested, but the basic structure of 'read a line, split it if there are commas, append it to the last field if there aren't' should be applicable in some form.