Separator in table concatenation

[Dirk Laurie <dirk.laurie@...>]

It would be nice if table.concat behaved like string.gsub:
   table.concat(tbl,sep)
would allow `sep` to be not only a string, but also a table or
function, indexed or called with the current list index.

E.g.
  tbl = {"A","B","C"}
  enumerate = function(k)
     return ", "..tostring(k+1)..": "
  end
  print("1: "..table.concat(tbl,enumerate))
1: A, 2: B, 3: C