What editor do you use? I use MacVim. If I were in your shoes, I'd just define a command that, besides commenting every line (i.e. by using [NERD Commenter](https://github.com/scrooloose/nerdcommenter)), would replace `//~` with some other distinctive token, and a second mapping to reverse this transformation. No need to complicate the parsing of `compiletest`, with a rule that works some of the time, but not all of the time.