Even if you're not allowing macros and code-as-data, you may want to consider Lisp-style S-expressions. It doesn't take long to get used to the parentheses, esp

Even if you're not allowing macros and code-as-data, you may want to consider Lisp-style S-expressions. It doesn't take long to get used to the parentheses, especially given that good Lisp code uses indentation to such an extent that most of the parentheses "disappear" for a human reader.