There might be a few others. https://github.com/google/wuffs https://github.com/google/wuffs for example isn't general purpose or mainstream, but it's meant to

There might be a few others. https://github.com/google/wuffs https://github.com/google/wuffs for example isn't general purpose or mainstream, but it's meant to solve practical problems, so I don't think I'd call it a research language. Opinions may vary.