I think so some local expression evaluation could be - but it should not be placed in \if statement
Why?
\expr issupported :VERSION_NUM >= 10000
Hmmm. Although I do not buy this, it could work as a replacement for \set which it seems cannot be upgraded because some people may rely on it to just store whatever comes after it in a variable.
I have no strong opinion on how expressive expressions should be, but having a separate \expr (or \setexpr, etc) gives us a green field to develop them.
