Even DRYer way!
@mixin box-shadow($args...) {
@each $pre in -webkit-, -moz-, -ms-, -o- {
#{$pre + box-shadow}: $args;
}
#{box-shadow}: #{$args};
}
And now you can reuse your box-shadow even smarter:
.myShadow {
@include box-shadow(2px 2px 5px #555, inset 0 0 0);
}