cfn-guard 3.2.0

AWS CloudFormation Guard is an open-source general-purpose policy-as-code evaluation tool. It provides developers with a simple-to-use, yet powerful and expressive domain-specific language (DSL) to define policies and enables developers to validate JSON- or YAML- formatted structured data with those policies.
Documentation 
1
2
3
4
5
6
7
8
9
10

let template = Resources.*[ Type == 'AWS::New::Service']

rule SOME_RULE when %template !empty {
    %template.Properties.Arn exists
    let arn = %template.Properties.Arn

    let res = substring(%arn, 0, 3)

    %res == "arn"
}