--- AWSTemplateFormatVersion: "2010-09-09" Description: > Test Join Functions Resources: myInstance: Type: AWS::EC2::Instance Properties: ImageId: ami-1234 UserData: Fn::Base64: Fn::Join: - '' - 'Test function' - 'another item' myInstance2: Type: AWS::EC2::Instance Properties: ImageId: ami-1234 UserData: Fn::Base64: Fn::Join: !Ref myInstance