Zygo does have infix available in addition to traditional lisp parentheses. Just put the math (or whatever) inside curly braces. I much prefer math in infix, so I put in a Pratt parser for that.
Wow. I have the exact opposite experience with TDD. I use TDD to set a specific goal, and to have the computer tell me almost instantly when I've reached it. Then I can unleash creativity in trying implementations, and know instantly if they've worked. Occassionally I'll get a lucky guess in that works. Such a great feeling knowing immediately that my intuition was right.
Google uses a subset of python called Starlark for build configuring (available in Go and I think Java). Nice if you want to be able to compute things during config.
Lua is fantastic for implementing languages. I did an implementation of Golang in it (https://github.com/gijit/gi). With metatables one can implement any kind of object/inheritance/interface scheme. Full builtin asymmetric coroutines, and a massively performant, ABI compatible backend (a just-in-time trace compiler) in LuaJIT are amazing tools.
Thank you. I tend to do interactive mathy things, and find the infix being the default at the repl cuts down on keystrokes and speeds up the interaction. Anything within {} curly braces is treated as infix, and infix is the starting mode at the repl. You can freely mix (prefix) and {infix} as you wish. For longer math expressions this does tend to help readability.