@import url(foo.css);
@media print {}
@media (min-width: 640px) and (min-height: 1000px) {}
@main-color: red;

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

[
	["atrule", [
		["rule", "@import"],
		["url", "url(foo.css)"],
		["punctuation", ";"]
	]],
	["atrule", [
		["rule", "@media"],
		" print"
	]],
	["punctuation", "{"],
	["punctuation", "}"],
	["atrule", [
		["rule", "@media"],
		["punctuation", "("],
		["property", "min-width"],
		["punctuation", ":"],
		" 640px",
		["punctuation", ")"],
		" and ",
		["punctuation", "("],
        ["property", "min-height"],
        ["punctuation", ":"],
        " 1000px",
        ["punctuation", ")"]
	]],
	["punctuation", "{"],
    ["punctuation", "}"],
	["atrule", [
		["rule", "@main-color"],
		["punctuation", ":"],
		" red",
		["punctuation", ";"]
	]]
]

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

Checks for at-rules.
Also checks for LESS variables.