code: func langEvalConfig(vs map[string]ast.Variable) *hil.EvalConfig {
  	funcMap := make(map[string]ast.Function)
  	for k, v := range Funcs() {
  		funcMap[k] = v
  	}
  	funcMap["lookup"] = interpolationFuncLookup(vs)
  	funcMap["keys"] = interpolationFuncKeys(vs)
  	funcMap["values"] = interpolationFuncValues(vs)
  
  	return &hil.EvalConfig{
  		GlobalScope: &ast.BasicScope{
  			VarMap:  vs,
  			FuncMap: funcMap,
  		},
  	}
  }
docs: // langEvalConfig returns the evaluation configuration we use to execute.