[c0nstantine]

>> E.g. what if I want to turn xyz into zYx?

echo 'zyx' | ./trre 'xy:Yz|zy:Yx'

It is still a regular language. I do not introduce references.

You are right in sense the `sed` is far superior editor. But here I see some advantages: - the current implementation is super small; it is direct translation to an automaton - the complex patterns may be compiled in a more efficient way using deterministic transducer. I can't defend this claim now but I have some evidences - there are some tricks you can do using 'generative' part of it, e.g. and you even can find levenshtein distance of 1 between two strings just by generating substitutions/insertions/deletions and implement a simple spell checker.

Overall, I think you have a good point. Maybe it is just marginal improvement (if any). It was more comfortable to write in this style instead of group usage. I used it for some time and found it handy (especially as extended `tr`).