The point is that prettiness is not easily defined.

As soon your array had too many, probably long entries, you'd complain again about a messed up long unreadable line.

That's why Data::Dump has a heuristic to inline short arrays with short entries.

IMHO you can only ask a feature request at the maintainer of JSON.pm.

 perl -MData::Dump -e'@a=("aaa","bbb","ccc"); @b=(@a)x4; dd \@a,\@b'
(
  ["aaa", "bbb", "ccc"],
  [
    "aaa",
    "bbb",
    "ccc",
    "aaa",
    "bbb",
    "ccc",
    "aaa",
    "bbb",
    "ccc",
    "aaa",
    "bbb",
    "ccc",
  ],
)
[download]

Data::Dumper OTOH doesn't have that heuristic, only global switches like you are asking for.

Do you see the problem?