- open the bundle editor and select the Actionscript bundle
- use the add button to make a new preference item, give it a scope of source.actionscript
- name it whatever
- paste in the following:

{   shellVariables = (
        {   name = 'TM_COMMENT_START';
            value = '// ';
        },
    );
}

- that's it! got these instructions on IRC from Infininight: http://pastie.textmate.org/private/clmfldbv2sexjcd7u6qjw

// Add this to your package..
import flash.text.*;

// And throw this in wherever..
var t:TextField = new TextField();
t.autoSize = TextFieldAutoSize.LEFT;
t.border = true;
addChild(t);

t.appendText("params:" + "\n");
try {
var key:String;
var val:String;
var flashvars:Object = LoaderInfo(this.root.loaderInfo).parameters;
for (key in flashvars) {
val = String(flashvars[key]);
t.appendText("\t" + key + ":\t" + val + "\n");
}
} catch (error:Error) {
t.appendText(error);
}