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

spruce.json

{"flavor":"1.29.0","prune":["meta"],"env":["HOME=/home/user","REDACT=''"],"cherry_pick":[],"yaml":[{"filename":"file1.yml","contents":"meta:\n  a: one\n  b: (( meta.a ))\n  c: (( grab meta.a ))\n\n\nout:\n  a: (( meta.a ))\n  a_grab: (( grab meta.a ))\n  b: (( meta.b ))\n  b_grab: (( grab meta.b ))\n  c: (( meta.c ))\n  c_grab: (( grab meta.c ))\n\n\n\n\n"}],"skip_eval":false,"fallback_append":false,"go_patch":false,"debug":true,"trace":false}