...
PageReference ref = ApexPages.currentPage();
Map<String,String> params = ref.getParameters();
HttpRequest req = new HttpRequest();
req.setEndpoint(params.get('url'));
HTTPResponse res = new Http().send(req);

string url = Request.Form["url"];
HttpClient client = new HttpClient();
HttpResponseMessage response = await client.GetAsync(url);

char *url = maliciousInput(); 
CURL *curl = curl_easy_init();
curl_easy_setopt(curl, CURLOPT_URL, url);
CURLcode res = curl_easy_perform(curl);

  ...
  final server = await HttpServer.bind('localhost', 18081);
  server.listen((request) async {
      final headers = request.headers;
      final url = headers.value('url');
      final client = IOClient();
      final response = await client.get(Uri.parse(url!));
      ...
  }

url := request.Form.Get("url")
res, err =: http.Get(url)
...

var http = require('http');
var url = require('url');

function listener(request, response){
  var request_url = url.parse(request.url, true)['query']['url'];
  http.request(request_url)
  ...
}
...
http.createServer(listener).listen(8080);
...

val url: String = request.getParameter("url")
val httpclient: CloseableHttpClient = HttpClients.createDefault()
val httpGet = HttpGet(url)
val response1: CloseableHttpResponse = httpclient.execute(httpGet)

$url = $_GET['url'];
$c = curl_init();
curl_setopt($c, CURLOPT_POST, 0);
curl_setopt($c,CURLOPT_URL,$url);
$response=curl_exec($c);
curl_close($c);

url = request.GET['url']
handle = urllib.urlopen(url)

url = req['url']
Net::HTTP.get(url)

def getFile(url: String) = Action { request =>
    ...
    val url = request.body.asText.getOrElse("http://google.com")

    ws.url(url).get().map { response =>
      Ok(s"Request sent to $url")
    }
    ...
}