Jump between footnote markers with Vim's * key

ToggleFootnoteJumping.vim

" Find related Pandoc footnote numbers
" -------------------------------------------------------------------
" Vim's * key searches for the next instance of the word under the 
" cursor; Vim decides what counts as the boundary of a word with the 
" iskeyword option. This function toggles the special characters of a 
" Pandoc footnote in the form [^1] to allow you to jump between 
" footnotes with the * key.
nnoremap _fn :call ToggleFootnoteJumping()<CR>
function! ToggleFootnoteJumping()
  if exists("g:FootnoteJumping") 
    if g:FootnoteJumping == 1
      set iskeyword-=[
      set iskeyword-=]
      set iskeyword-=^
      let g:FootnoteJumping = 0
    else
      set iskeyword+=[
      set iskeyword+=]
      set iskeyword+=^
      let g:FootnoteJumping = 1
    endif
  else 
    set iskeyword+=[
    set iskeyword+=]
    set iskeyword+=^
    let g:FootnoteJumping = 1
  endif
endfunction