$foo
$Foobar_42
$::foo
$foo::bar42

${foobar}

set foo bar
set Foobar_42 baz
set ::foo bar
set foo::bar42 baz

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

[
	"$", ["variable", "foo"],
	"\r\n$", ["variable", "Foobar_42"],
	"\r\n$", ["variable", "::foo"],
	"\r\n$", ["variable", "foo::bar42"],

	"\r\n\r\n$", ["variable", "{foobar}"],

	["keyword", "set"], ["variable", "foo"], " bar\r\n",
	["keyword", "set"], ["variable", "Foobar_42"], " baz\r\n",
	["keyword", "set"], ["variable", "::foo"], " bar\r\n",
	["keyword", "set"], ["variable", "foo::bar42"], " baz"
]

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

Checks for variables.