[racket] Scribble: collapse index entries

Is it possible to get Scribble to collapse index entries to the same 
key, so that instead of

foo, 1
foo, 2

you'd get

foo, 1, 2

or better

foo, 1-2

?

Thanks,
David

#lang scribble/manual

@section{First page}
@as-index{foo}

@section{Second page}
@as-index{foo}

@index-section[]