Problem:
The loading of a .md file was slow due to multiple nested lookback.
It is advised in vim help to prefer \zs, see :h /\@<
Anyway, it is useless to nest them.
089.080 000.085 000.085: sourcing /home/mtourneb/.vim/after/syntax/vimwiki.vim
089.264 005.184: opening buffers
089.322 000.058: BufEnter autocommands
089.323 000.001: editing files in windows
089.414 000.091: VimEnter autocommands
089.415 000.001: before starting main loop
303.698 214.283: first screen update
303.700 000.002: --- VIM STARTED ---
Solution:
Remove the function s:expand_delimiter in vars.vim.
It was doing a duplicate job with vimwiki#u#hi_expand_regex
And ... well avoid lookback as much as possible
091.784 000.087 000.087: sourcing /home/mtourneb/.vim/after/syntax/vimwiki.vim
091.991 006.034: opening buffers
092.050 000.059: BufEnter autocommands
092.052 000.002: editing files in windows
092.172 000.120: VimEnter autocommands
092.173 000.001: before starting main loop
112.574 020.401: first screen update
112.578 000.004: --- VIM STARTED ---