It's programming language that distinguishes between spaces and tabs in a way that changes behavior. It's also the only PL that I know of that's outright incompatible with expand-all-tabs-to-spaces editing policy, which is what the vast majority of coders use in practice.

If you want to see a powerful and actually simple tool that does the job, take a look at DJB redo: https://redo.readthedocs.io/en/latest/