This speeds up `DefaultReplacements` by a lot (order of magnitude or so), speeding up my entire compilation by 1 ms=0.02%. Also, this prevents it from hanging and/or slowly dying on `-Fu$oops$` where environment variable `oops` contains “`$oops$`”. On the other hand, this considerably changes the behaviour in the case of nested expansions, but _probably_ won’t break anything. In particular, macros inside environment variables are now expanded too (can easily be prohibited, but why would you). [DefaultReplacements.patch](/uploads/12c56ec65a0cb32a252cc647d553c5a0/DefaultReplacements.patch)