less 里面 opacity的写法

今天写了个opacity， 竟然less编译不过，上网搜了一个写法

.opacity (@opacity) {
    @opacityPercentage: @opacity * 100;
    opacity: @opacity;
    -ms-filter: ~"progid:DXImageTransform.Microsoft.Alpha(opacity=(@{opacityPercentage}))"; 
    filter: ~"alpha(opacity = (@{opacityPercentage}))";
}

in dotless 1.2.3

.opacity (@opacity) {
    @opacityPercentage: @opacity * 100;
    opacity: @opacity;
    -ms-filter: progid:DXImageTransform.Microsoft.Alpha(opacity=(@opacityPercentage)); 
    filter: alpha(opacity = (@opacityPercentage));
}