function linkCPAN() {
    let codes = document.getElementsByClassName('codetext');
    // let pattern = '$1<href="http://search.cpan.org/perldoc?$3">$3</a>';
    let replacer = function (match, p1, p2, p3) {
        return p1 + '<href="http://search.cpan.org/perldoc?' + p3 + '">' + p3 + '</a>';
    };
    for (var i in codes) {
        if (!codes.hasOwnProperty(i)) continue;
        let text = codes[i];
        let inner = text.innerHTML;
        inner = inner.replace(/((use|require)\s+)((\w+)(::\w+)*)/g, replacer);
        console.log(inner);
        text.innerHTML = inner;
    }
}