If you think of well-defined as combining the most subtle aspects of Javascript semicolons and Python braces, I agree. As hobby projects, I have coded a signifi

If you think of well-defined as combining the most subtle aspects of Javascript semicolons and Python braces, I agree. As hobby projects, I have coded a significant fraction of a Haskell parser and a majority of a Python parser. It was good I did the Python one first. The Haskell rules include a clause which says if you don't yet have a syntax error from your tokens, and you have a syntax error by adding the next token, and you would not have a syntax error if you added first a closing brace and then the next token, then insert the corrective closing brace. So you can't just tokenize, infer what's missing, then parse the tokens.