[gucci-on-fleek]

> except for a programming language instead of TeX

TeX is a programming language. It's not a very good programming language, but people have implemented floating-point math [0], regular expressions [1], an Arduino emulator [2], and terminal input/output [3] in pure TeX. The last two examples are obscure, but the first two examples are used (internally) by the vast majority of modern LaTeX documents.

[0]: https://github.com/latex3/latex3/blob/develop/l3kernel/l3fp....

[1]: https://github.com/latex3/latex3/blob/develop/l3kernel/l3reg...

[2]: https://www.ctan.org/pkg/avremu

[3]: https://www.ctan.org/pkg/reverxii