Ah, a very simple and clever "why didn't I think of that?" solution, thanks. If I were to go that route I'd probably use nano as it's more straightforward if you just do simple editing. It won't quite work for me though as I don't want the editor to take up the whole screen so user can compare/copy/paste other printed text above it (I'm not just writing an editor, but using it as a component of a specialized tool.) I could use vim/split screen, though this gets clumsy (back to vim modes/commands complexity, manually have to remember the filename to open in :split, yada yada) and I want the user to be able to simply answer a "do you want..." and immediately have the display I want. Anyway, not the UX I'm looking for.

Good simple suggestion though without knowing all the details of my needs.

And even academically, I would like to know the answer to the op using core perl.