Using Vim, how do you use a variable to store count of patterns found?

Question

This question was helpful for getting a count of a certain pattern in Vim, but it would be useful to me to store the count and sum the results so I can echo a concise summar

Answer 1

I think that answer above is hard to understand and more pretty way to use external command grep like this:

:let found=0
:bufdo let found=found+(system('grep "
" '.expand('%:p') . '| wc -l'))
:echo found