[Vuejs]-Module build failed when trying to globally import variables on Laravel Vue project

Just hit the same issue, turned out I was omitting the semicolon in my global definitions.
Try giving this a go:

{
    test: /\.scss$/,
    use: [
        "vue-style-loader",
        "css-loader",
        {
            loader: "sass-loader",
            options: {
                data: `@import "@/_var.scss;` //<- Semicolon here.
            }
        }
    ]
}