" something that won't be met anywhere
let s:sep = "₀◎○ë"

function! align#do(first, last, sep) abort
    let in = []
    for n in range(a:first, a:last)
        let in = add(in, substitute(getline(n), a:sep, "\t" . s:sep, "g"))
    endfor
    let out = systemlist("column -t -s \"\t\"", add(in, ""))
    for n in range(a:first, a:last)
        call setline(n, substitute(out[n - a:first], "  " . s:sep, a:sep, "g"))
    endfor
endfunction