patch 8.2.1502: Vim9: can use += with a :let command at script level Commit: https://github.com/vim/vim/commit/122616d9c1b57f1e1f29f1151f8e26d24df9092a Author: Bram Moolenaar <Bram@vim.org> Date: Fri Aug 21 21:32:50 2020 +0200 patch 8.2.1502: Vim9: can use += with a :let command at script level Problem: Vim9: can use += with a :let command at script level. Solution: Give an error.

" This script makes a tags file for help text.
"
" Usage: vim -eX -u doctags.vim

try
  helptags ++t .
  echo 'help tags updated'
catch
  echo v:exception
  echo 'help tags failed update'
endtry
echo ''
qa!