When mapping is performed multiple times in vim selection mode

  question, vim
function Hello()
 echo "hello world\n"
 map <leader>w :call Hello()<CR>

Under normal mode, I press<leader>W calls the Hello () function once, but if I call the Hello () function n times in the selection mode, the number of times n is the same as the number of rows selected. if I want to call the function only once in the selection mode now, what should I do?

Scope of self-handling:

function Hello() range


:help :call