[tialaramex]

> I thought substring operations worked on characters

"character" turns out to be too vague an idea to correspond to some specific fact about the software. If you co-worker says his Uncle is "conservative" does he mean like "Believes Right To Work laws are a good idea" conservative or "Believes Joe Biden is a Communist" conservative ?

https://en.wikipedia.org/wiki/Character_(symbol) gives you some idea about this rabbit hole. Suffice to say, no, you can't have operations on "characters" until you've nailed down exactly what it was you meant by that.