On Sun, 2 Aug 2015, Idris Samawi Hamid ادريس سماوي حامد wrote:

> But I'll bet Hans could figure out a way to do it in lua.

If you need this to happen before macro expansion, then there are two 
options: use input translation (see, for example, the m-translate module) 
or capture the entire content in a buffer and use Lua to do the 
appropriate substitutions (see, 
http://wiki.contextgarden.net/Programming_in_LuaTeX#Manipulating_verbatim_text)

Both these methods will miss things like: one paragraph \par second 
paragraph, etc.

Aditya