pre[class*=language-] {
    position: relative
}

    pre[class*=language-][data-language]::before {
        content: attr(data-language);
        color: #000;
        background-color: #CFCFCF;
        display: inline-block;
        position: absolute;
        top: 0;
        right: 0;
        font-size: .9em;
        border-radius: 0 0 0 5px;
        padding: 0 .5em;
        text-shadow: none
    }