packer-cn/packer/test-fixtures/build-variables-interpolate.json

{
    "variables": {
    	"foo":  "bar",
		"bar":  "{{user `foo`}}",
		"baz":  "{{user `bar`}}baz",
		"bang": "bang{{user `baz`}}"
	},
	"builders": [
        {"type": "foo"}
    ]
}