Writing Variables into XML

How can I write variables into new XML? I need to take variables and write them into new XML but that I am getting is the name of the variable I am using, not the value.


var _label:String = _set.attribute( "containing" ).toString();
_subMenuItems.appendChild( XML(<item><label>_label</label></item> ) );

//
// Outputs 
<item><label>_label</label></item>