Print "Verifying the contents again";
   .
   .
   .
   Print "Verifying the output to be shown"; // line 2

set completefunc=CompleteInsideSymbols
function! CompleteInsideSymbols(findstart, base) abort
    if a:findstart
        let start = col('.') - 1
        let line = getline('.')
        while start > 0 && line[start - 1] !~ "["'[]"
            let start -= 1
        endwhile
        return start
    else
        let groups_of_words = []
        %s/v("zs.{-}ze"|'zs.{-}ze'|[zs.{-}ze])/=add(groups_of_words,submatch(0))/gn
        return filter(groups_of_words, 'v:val =~ "^" . a:base')
    endif
endfunction

if a:findstart
    ...
else
    ...
endif

let start = col('.') - 1
    let line = getline('.')

while start > 0 && line[start - 1] !~ "["'[]"
        let start -= 1
    endwhile

return start

let groups_of_words = []

%s/v("zs.{-}ze"|'zs.{-}ze'|[zs.{-}ze])/=add(groups_of_words,submatch(0))/gn

return filter(groups_of_words, 'v:val =~ "^" . a:base')

here is " a group of quoted words " and here is " another one "

" an