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This article aims to demonstrate some of the many uses of the Fn::Sub syntax in the AWS CloudFormation service. Topics include:
Basic Fn::Sub and !Sub syntax
Short and long form syntax
Nested Sub and ImportValue statements
BACKGROUND
About a year ago (Sept 2016, along with YAML support) AWS added a new intrinsic function to CloudFormation: Fn::Sub. This greatly improved string concatenation in CloudFormation.
