va.scss

@mixin box-shadow($arg) {
	-moz-box-shadow: $arg;
	-ms-box-shadow: $arg;
	-o-box-shadow: $arg;
	-webkit-box-shadow: $arg;
	box-shadow: $arg;
}

div {
//	Mixin box-shadow takes 1 argument but 2 were passed. (Sass::SyntaxError)
//	@include box-shadow(0 0 5px red, 0 0 5px blue inset);

	@include box-shadow((0 0 5px red, 0 0 5px blue inset));
}