var myExt={
    foo:function(){}
};

Components.utils.import( "resource://myExt/modules/myExt.jsm" myExt );

myExt.bar.meh(); //call the exported object


///end of regular javascript

inside myExt.jsm is:

var EXPORTED_SYMBOLS = ["bar"];

var bar:{
    meh:function(){
        myExt.foo();    //do I have access to this?
    }
};