/*
 * call-seq:
 *   Curl::Easy.perform(url) { |easy| ... }           => #<Curl::Easy...>
 *
 * Convenience method that creates a new Curl::Easy instance with
 * the specified URL and calls the general +perform+ method, before returning
 * the new instance. For HTTP URLs, this is equivalent to calling +http_get+.
 *
 * If a block is supplied, the new instance will be yielded just prior to
 * the +http_get+ call.
 */
static VALUE ruby_curl_easy_class_perform(int argc, VALUE *argv, VALUE klass) {