execute multiple statements with variable passing in script tag

due to the EnvironmentBindings.java, it is not possible to execute script like below (javascript):

var b = "value b";
var c = b;

scriptEngine will report error like

sun.org.mozilla.javascript.internal.EcmaError: ReferenceError: "b" is not defined. (<Unknown source>#4) in <Unknown source> at line number 4

because EnvironmentBindings never accept new variable passed to it.