BTW, when merging can I delete some keys? Something like:

# parent.yaml
foo:
  bar: 2
  baz: 3

# child.yaml
foo:
  bar: 4 # override foo/bar
  *baz: whatever # undefine baz, prompt users to choose
[download]

OR baz: delete!

I don't see that option in Hash::Merge. Other module, perhaps?