Can mediator append XML via a function like bpelx:append?

In the reply portion of a mediator rule, I am trying to assign an XML element as the first child of a target parent element whose content type is xsd:anyType.

So, I want to assign <MyResponse><FirstChild>hello</FirstChild></MyResponse>

to <content><MyResponse><FirstChild>hello</FirstChild></MyResponse><content>  (where <content> is xsd:anyType).

Using the regular <copy> function, the result comes out as:

<content><FirstChild>hello</FirstChild><content>

In BPEL, I achieve the correctly-generated XML via <bpelx:append> instead of <copy>.

Is there an analogous way to do this in Mediator?

Thank you,

Michael