gistfile1.sass

// Source: http://ianstormtaylor.com/oocss-plus-sass-is-the-best-way-to-css/

// Sass
%separator
    border-top: 1px solid black
hr
    @extend %separator
.separator
    @extend %separator

// Compiled Sass to CSS
hr,
.separator {
    border-top: 1px solid black
}

// Less equivalent
.sep {
    border-top: 1px solid black;
}
hr,
.separator {
    .sep;
}

// Compiled Less to CSS
.sep {
    border-top: 1px solid black;
}
hr,
.separator {
    border-top: 1px solid black;
}