Oh, please, this is a really awesome feature! With this feature, you will be able to control the aspect of your page in a reactive way, based on determined conditions.

SASS example:

@if lightness($my-color) > 90% {
  background-color: #FF0000;
}

@else {
  background-color: #00FF00;
}

In LESS, the things are not similar. You need to use CSS guards:

.mixin (@my-color) when (lightness(@my-color) >80%) {
  background-color: #00FF00;
}
.mixin (@my-color) when (lightness(@my-color) =< 80%) {
  background-color: #FF0000;
}

These are not all the preprocessor features, but at this moment, they're enough to start working on our FIFA World Cup application!