my test:
test words: `ahead`,`browser`,`abot`,`date`,`effie`,`fabian`,`YouTube`,`zebedee`
built-in `system` is only tiny faster
````vimL
function! s:test1()
   let c = 0
   while c < 100
       let a = system("look ahead | head -n 30")
       let a = system("look browser | head -n 30")
       let a = system("look cabot | head -n 30")
       let a = system("look date | head -n 30")
       let a = system("look effie | head -n 30")
       let a = system("look fabian | head -n 30")
       let a = system("look YouTube | head -n 30")
       let a = system("look zebedee | head -n 30")
       let c = c + 1
   endwhile
endfunction

function! s:test2()
   let c = 0
   while c < 100
       let a = neocomplcache#util#system("look ahead | head -n 30")
       let a = neocomplcache#util#system("look browser | head -n 30")
       let a = neocomplcache#util#system("look cabot | head -n 30")
       let a = neocomplcache#util#system("look date | head -n 30")
       let a = neocomplcache#util#system("look effie | head -n 30")
       let a = neocomplcache#util#system("look YouTube | head -n 30")
       let a = neocomplcache#util#system("look zebedee | head -n 30")
       let c = c + 1
   endwhile
endfunction

let start1 = reltime()
call s:test1()
echomsg "built-in: ".reltimestr(start1)

let start2 = reltime()
call s:test2()
echomsg "neo:       ".reltimestr(start2)

```

**result**:
round 1

    built-in:    1369204196.830606
    neo:        1369204223.499835

round 2

    built-in:    1369205157.941404
    neo:        1369205184.674097