Adding Guzzle Client Middleware to use proxy based on request URL in Laravel

Question

I'm using Guzzle HTTP client for making requests from my Laravel 10 application. I want to use a proxy for some URLs, thought about doing so with middleware. Thing is, in order to intercept the request and check its URL I already created a middleware. Then, if I add a middleware from the previous one's callback, I'll be adding it on every call, and the first one seems to skip the proxy.

My current code:

$stack = HandlerStack::create();

$stack->push(Middleware::mapRequest(function (RequestInterface $request) use ($stack) {
    if (strpos($request->getUri(), "string") !== false) {
        $stack->push(function (callable $handler) use ($proxy) {
            return function (RequestInterface $request, array $options) use ($handler, $proxy) {
                $options['proxy'] = $proxy;
                return $handler($request, $options);
            };
        });

    }

    return $request;
});

$client = new Client(['handler' => $stack]);

Any idea how I can make it work from the first call, without pushing the same middleware over and over?