reverse(str)

function explode(e, sep)
    local result = {}    e:gsub("[^".. sep .."]+", function(s) table.insert(result, s:match("^%s*(.-)%s*$")) end)
    return result
end

function reverse(str)
    local ret = {}
    local T = explode(str, " ")

    for i = #T, 1, -1 do
          table.insert(ret, T[i])
    end

    return table.concat(ret, " ")
end