How to set the tablabel in vim

guitablabel.vim

"
" Guitablabels
"
let t:tablabel="<>"
function! GuiTabLabel()
  if exists("t:tablabel")
    return t:tablabel
  else
    return expand("%f") 
    " or do something more clever
    return substitute( expand("%f"), '\([^/]\)[^/]*/', '\1../', "g" )
  endif
endfunction

set guitablabel=%{GuiTabLabel()}


"
" application example:
"

function OpenTabWithLabel( path, label )
  let t:tablabel=a:label
  exe "tabnew " . a:path
endfunction