I’ve seen these a few times but only today decided to actually work out how they worked.
YAML lets you define an anchor (
&name) for a node, sequence or scalar that you can refer
to later with an alias (
*name). This lets you avoid duplication by extending or
twin1: &person first: Barry last: Chuckle twin2: <<: *person first: Paul
For more, see http://blogs.perl.org/users/tinita/2019/05/reusing-data-with-yaml-anchors-aliases-and-merge-keys.html