ExpandHelpWord()

gistfile1.vim

" Help terms can include characters typically not considered within keywords.
function! ExpandHelpWord()
  let iskeyword = &iskeyword
  set iskeyword=!-~,^),^*,^\|,^",192-255
  let word = expand('<cword>')
  let &iskeyword = iskeyword
  return word
endfunction

" F1 to show context sensitive help for keyword under cursor
" Deliberately left off the terminating <cr> to allow modification.
" Moves the cursor to the beginning of the term for contextual markup.
" (:help help-context)
nnoremap <F1> :help <c-r>=ExpandHelpWord()<cr><c-left>