curl "Unknown error" when using Net::Curl::Easy and "pushopt" options

I need to pass authorization data to the proxy. However, this code (see below) results in an error.

#!/usr/bin/perl -w

$| = 1;

use Net::Curl::Easy qw(:constants);
 
my $easy = Net::Curl::Easy->new();
$easy->setopt( CURLOPT_URL, "https://checkip.amazonaws.com/" );
$easy->setopt( CURLOPT_VERBOSE, 1 );
$easy->setopt( CURLOPT_PROXY_SSL_VERIFYPEER , 0 );
$easy->setopt(CURLOPT_PROXY_SSL_VERIFYHOST, 0);
$easy->setopt(CURLOPT_SSL_VERIFYPEER, 0);
$easy->setopt(CURLOPT_USERAGENT, "curl");
$easy->setopt(CURLOPT_PROXY, "http://35.244.25.186:3128"); # some proxy
$easy->setopt(CURLOPT_HEADER, 1);
$easy->pushopt(CURLOPT_PROXYHEADER, ['username: apikey']); # when set "HTTPHEADER", everything is work fine

$easy->perform();

Tried to change proxyheader to httpheader, no errors. But, the header is sent to both the proxy and the target server, which does not suit me, since it is necessary that the header be sent only to the proxy.

Thank you in advance.

P.S. Python code that works similarly does not cause errors.

import sys
import pycurl

c = pycurl.Curl()
c.setopt(c.URL, 'https://checkip.amazonaws.com/')
c.setopt(c.VERBOSE, 1)
c.setopt(c.PROXY_SSL_VERIFYPEER , 0)
c.setopt(c.PROXY_SSL_VERIFYHOST, 0)
c.setopt(c.SSL_VERIFYPEER, 0)
c.setopt(c.USERAGENT, "curl")
c.setopt(c.PROXY, "http://35.244.25.186:3128")
c.setopt(c.PROXYHEADER, ['a: b'])
c.perform()

This looks like a bug to me in Net::Curl. CURLOPT_HTTPHEADER and CURLOPT_PROXYHEADER should be treated both as a list. But CURLOPT_PROXYHEADER wasn't specifically treated, so it likely was used as an integer argument only which broke pushopt (since no list) and caused a segmentation fault with setopt (since a list was treated as an integer).

Patch for fixing the issue can be found on the bug report recently opened (likely by the OP): https://github.com/sparky/perl-Net-Curl/issues/73#issuecomment-1588512766:

--- a/Curl_Easy.xsh
+++ b/Curl_Easy.xsh
@@ -29,6 +29,7 @@ typedef enum {
 
 static const CURLoption perl_curl_easy_option_slist[] = {
        CURLOPT_HTTPHEADER,
+       CURLOPT_PROXYHEADER,
        CURLOPT_HTTP200ALIASES,
 #ifdef CURLOPT_MAIL_RCPT
        CURLOPT_MAIL_RCPT,