a bit o' spruce, from http://play.spruce.cf

spruce.json

{"flavor":"1.16.2","prune":["meta"],"env":["HOME=/home/user"],"cherry_pick":[],"yaml":[{"filename":"file1.yml","contents":"--- # kit\nmeta:\n  default:\n    azs: [z1, z2, z3]\n    \n"},{"filename":"file2.yml","contents":"--- # kit-part-2\nproperties:\n  azs: (( grab params.availability_zones || meta.default.azs ))\n"}],"skip_eval":false,"fallback_append":false,"go_patch":false,"debug":false,"trace":false}