function solution(input, cmd)

  -- parse all <name>="<bla>" (key/value pairs)

  local i, values, pos = 0, {}, {}

  local j, k, v

  while true do

    j, i, k, v = string.find(input, '([a-zA-Z]+)="([^"]*)"', i+1)

    if not j then break end

    values[k] = v

    pos[k] = {j+#k+2, i}

  end

  -- cmd = "copy <key1> to <key2>"

  local key1, key2 = cmd:match("copy ([%S]+) to ([%S]+)")

  if not key1 then error("Could not parse command: "..cmd) end

  -- look up key1

  local value = values[key1]

  if not value then error("attribute "..key1.." not found") end

  -- paste after key2 in input (removing the old value)

  if not pos[key2] then error("attribute "..key2.." not found") end

  local i, j = unpack(pos[key2])

  input = input:sub(1, i-1)..value..input:sub(j)

  return input

end