It is legal CSV - the only thing goofy about it is that it has a semicolon on one of the places between commas, rather than useful header or data information. If I'm blindly using your new approach to read CSV files because, for example, I'm an unwitting recipient of the file, or because (more likely) I've forgotten about the format, I'd like the autodetect to warn me "Hey, this isn't quite standard CSV". I don't have a problem reading the data - we just read a whole line, use a regex to split it at the semicolon and away we go. It's intended as an example of something that will trip up a user of your autodetect. The lines in the file are long enough that a lazy user would look at the upper left and say "looks like CSV, I'll apply my generic CSV reader that use's Tux's nifty autodetect"