vim 下 :help internal-variables
buffer-variable b: Local to the current buffer.
window-variable w: Local to the current window.
tabpage-variable t: Local to the current tab page.
global-variable g: Global.
local-variable l: Local to a function.
script-variable s: Local to a |:source|’ed Vim script.
function-argument a: Function argument (only inside a function).
vim-variable v: Global, predefined by Vim.