@unknown;
@unknown x y;
@unknown "blah";
@unknown \"blah\";
/*@unknown!*test*!;*/
/*@unknown!*test*!x!*test*! y;*/
@unknown  ;
@unknown  x  y;

@unknown {}
@\unknown {}
@unknown a b {}
@unknown {p:v}
@unknown x y {p:v}
/*@unknown x, y x(1) {p:v}*/
/*@unknown x, y x(1+2) {p:v}*/
@unknown/*test*/{/*test*/p/*test*/:/*test*/v/*test*/}
/*@unknown!*test*!x!*test*! y!*test*!{!*test*!p!*test*!:!*test*!v!*test*!}*/
/*@unknown!*test*!x!*test*!,!*test*!y!*test*! x(!*test*!1!*test*!+!*test*!2!*test*!)!*test*!{!*test*!p!*test*!:!*test*!v!*test*!}*/
@unknown  {  p  :  v  }
@unknown  x  y  {  p  :  v  }
/*@unknown  x  ,  y  x(  1  +  2  )  {  p  :  v  }*/

@unknown {s{p:v}}
@unknown x y {s{p:v}}
/*@unknown x, y f(1) {s{p:v}}*/
/*@unknown x, y f(1+2) {s{p:v}}*/
@unknown { .a { p: v; } .b { p: v } }
@unknown/*test*/{/*test*/s/*test*/{/*test*/p/*test*/:/*test*/v/*test*/}/*test*/}
/*@unknown!*test*!x!*test*! y!*test*!{!*test*!s!*test*!{!*test*!p!*test*!:!*test*!v!*test*!}!*test*!}*/
/*@unknown!*test*!x!*test*!,!*test*!y!*test*! f(!*test*!1!*test*!+!*test*!2!*test*!)!*test*!{!*test*!s!*test*!{!*test*!p!*test*!:!*test*!v!*test*!}!*test*!}*/
@unknown  {  s  {  p  :  v  }  }
@unknown  x  y  {  s  {  p  :  v  }  }
/*@unknown  x  ,  y  f(  1  )  {  s  {  p  :  v  }  }*/
/*@unknown  x  ,  y  f(  1    2  )  {  s  {  p  :  v  }  }*/

@unknown {
    --> {}
    <!-- {}
}

@unknown {
    @unknown {s{p:v}}
}

@unknown {
    @unknown {s{p:v}}
    
    color: red;
}

.foo {
    @unknown {s{p:v}}

    color: red;
}