ViM Syntax File Syn Match using Perl RegEx

Question

I was wondering if it's possible to use a Perl RegEx in a .vim syntax file instead of Vim Speak.

If I have a syntax file such as

/usr/share/vim/vim80/syntax/none.vim

" Vim syntax file
" Language:     Custom None
" Maintainer:   Nobody

if exists("b:current_syntax")
  finish
endif

syn match noneIndentError "*Some Vim Speak RegEx*"

hi def link noneIndentError Error

let b:current_syntax = "none"

Is it possible to use a Perl RegEx inside of the syn match instead of a Vim Speak one? My RegEx is written for Perl and I can't seem to get it to work in Vim Speak

(?:^)(?: {4})*+( {1,})

The RegEx just tests for spaces that aren't included in the indented 4 spaces, you can see it here if you'd like

https://regex101.com/r/oBCjY4/1

Answer 1

The following match should do what you want:

syn match noneIndentError /^\( \{4\}\)*\zs \{,3\}/

Using \zs, you can exclude the pattern before it from the match, so it's a simpler way to write zero-width look-arounds (it's similar to \K in Perl). Then it matches up to 3 spaces.

Here's how it matches various lines:

      foo #
   bar
     
    
        baz

1. 6 spaces followed by text
2. 3 spaces followed by text
3. 5 spaces
4. 4 spaces
5. 8 spaces followed by text