This sub-thread effectively underscores why it's such a Good Idea to use modules. There are numerous edge cases that make this a difficult problem. Chief among them: what about empty fields? Certainly they should be possible, so you can't just grep them out. But you don't want to introduce them, either.
Then there's the issue about quoting quotes, which wasn't mentioned in this problem, but would probably come up eventually in any real-world case that gets used much. And reporting errors on malformed lines.
That said, I've got a regex that at least seems to deal with the empty fields properly:
A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James