24130053.less

.sprite-resize(@file) {
    .sprite-ret('@sprite-retina-@{file}');
    .sprite-norm('@sprite-@{file}');
}

.sprite-ret(@ret) {
    background-image: url(@ret);
}

.sprite-norm(@norm) {
    .lt-ie9 & {
        background-image: url(@norm);
    }
}

// test

.test {
    .sprite-resize(facebook);
}