$foo
$foo[bar]
$foo_bar[
	$.baz[foo]
	$.1[bar]
]
$foo.$bar
$foo.[$bar.baz]
$math:PI

($foo)

<div class="$foo">

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

[
	["variable", ["$foo"]],
	["variable", ["$foo"]], ["punctuation", "["], "bar", ["punctuation", "]"],
	["variable", ["$foo_bar"]], ["punctuation", "["],
	["variable", ["$", ["punctuation", "."], "baz"]],
	["punctuation", "["], "foo", ["punctuation", "]"],
	["variable", ["$", ["punctuation", "."], "1"]],
	["punctuation", "["], "bar", ["punctuation", "]"],
	["punctuation", "]"],
	["variable", ["$foo", ["punctuation", "."]]], ["variable", ["$bar"]],
	["variable", ["$foo", ["punctuation", "."]]], ["punctuation", "["],
	["variable", ["$bar", ["punctuation", "."], "baz"]], ["punctuation", "]"],
	["variable", ["$math", ["punctuation", ":"], "PI"]],

	["expression", [
		["punctuation", "("],
		["variable", ["$foo"]],
		["punctuation", ")"]
	]],

	["tag", [
		["tag", [
			["punctuation", "<"],
			"div"
		]],
		["attr-name", ["class"]],
		["attr-value", [
			["punctuation", "="],
			["punctuation", "\""],
			["variable", ["$foo"]],
			["punctuation", "\""]
		]],
		["punctuation", ">"]
	]]
]

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

Checks for variables.