gistfile1.txt

My attempt (bad):

    function s:FixWhitespace() range
        for lineno in range(a:firstline, a:lastline)
            call setline(lineno, substitute(getline(lineno), '\s\+$', '', ''))
        endfor
    endfunction

    " Run :FixWhitespace to remove end of line white space.
    command! -range=% FixWhitespace silent! <line1>,<line2>call <SID>FixWhitespace


Original command (works):

    command! -range=% FixWhitespace silent! let savesearch = @/ | keepjumps <line1>,<line2>substitute/\s\+$// | let @/ = savesearch | unlet savesearch