Multiple variable assignment in a command

Question

I have a function that outputs on stdout as well as on stderr. E.g.

function test(){
   echo "out"
   echo "err" >&2
}

Now, calling this function, who can I redirect both output pipes to different bash variables? So it should work as the following line

f=`tempfile`
x=`test 2>"$f"`
y=`cat "$f"`

but without having to redirect on pipe into a file. Thanks a lot in advance!