patch 8.2.4515: old subsitute syntax is still supported Commit: https://github.com/vim/vim/commit/9fb7b42935f13b5d3407eb82b151da1e9b4b6048 Author: Bram Moolenaar <Bram@vim.org> Date: Sat Mar 5 21:13:26 2022 +0000 patch 8.2.4515: old subsitute syntax is still supported Problem: Old subsitute syntax is still supported. Solution: Disallow using backslash after ":s" in Vim9 script.

" Simplistic way to make spaces and Tabs visible

" This can be added to an already active syntax.

syn match Space " "
syn match Tab "\t"
if &background == "dark"
  hi def Space ctermbg=darkred guibg=#500000
  hi def Tab ctermbg=darkgreen guibg=#003000
else
  hi def Space ctermbg=lightred guibg=#ffd0d0
  hi def Tab ctermbg=lightgreen guibg=#d0ffd0
endif