The utpl script language supports declaring arrays using JSON notation.

-- Expect stdout --
[ ]
[ "first", "second", 123, [ "a", "nested", "array" ], { "a": "nested object" } ]
-- End --

-- Testcase --
{%
	// An empty array can be declared using a pair of square brackets
	empty_array = [ ];

	// JSON notation is used to declare an array with contents
	json_array = [
		"first",
		"second",
		123,
		[ "a", "nested", "array" ],
		{ a: "nested object" }
	];

	// Printing (or stringifying) arrays will return their JSON representation
	print(empty_array, "\n");
	print(json_array, "\n");
-- End --