carto/test/rendering/cross_stylesheet_variable.mml

{
    "srs": "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over",
    "Stylesheet": [
        "cross_stylesheet_variable_a.mss",
        "cross_stylesheet_variable_b.mss"
    ],
    "Layer": [{
        "name": "world",
        "srs": "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over",
        "Datasource": {
            "file": "http://tilemill-data.s3.amazonaws.com/test_data/shape_demo.zip",
            "type": "shape"
        }
    }]
}