${testString?upper_case}
${testString?html}
${testString?upper_case?html}

${testSequence?size}
${testSequence?join(", ")}

----------------------------------------------------

[
	["ftl", [
		["ftl-interpolation", [
			["punctuation", "${"],
			["content", [
				"testString",
				["operator", "?"],
				["builtin-function", "upper_case"]
			]],
			["punctuation", "}"]
		]]
	]],
	["ftl", [
		["ftl-interpolation", [
			["punctuation", "${"],
			["content", [
				"testString",
				["operator", "?"],
				["builtin-function", "html"]
			]],
			["punctuation", "}"]
		]]
	]],
	["ftl", [
		["ftl-interpolation", [
			["punctuation", "${"],
			["content", [
				"testString",
				["operator", "?"],
				["builtin-function", "upper_case"],
				["operator", "?"],
				["builtin-function", "html"]
			]],
			["punctuation", "}"]
		]]
	]],

	["ftl", [
		["ftl-interpolation", [
			["punctuation", "${"],
			["content", [
				"testSequence",
				["operator", "?"],
				["builtin-function", "size"]
			]],
			["punctuation", "}"]
		]]
	]],
	["ftl", [
		["ftl-interpolation", [
			["punctuation", "${"],
			["content", [
				"testSequence",
				["operator", "?"],
				["builtin-function", "join"],
				["punctuation", "("],
				["string", [
					"\", \""
				]],
				["punctuation", ")"]
			]],
			["punctuation", "}"]
		]]
	]]
]

----------------------------------------------------

Checks for builtin functions.
