Hi all,

I currently have quite some scripts running on Perl 5.24 on a Microsoft Windows Server running IIS 10.0. On this server I use a certificate to for HTTPS connections. The scripts are all using the CGI.pm module to do CGI. As I do use Non-Parsed Headers (NPH), all my scripts start with the prefix "nph-" and have the following line to import the CGI module:

use CGI qw/:standard -nph/;
[download]

Now when a browser requests one of my scripts, these scripts are executed twice. I have made a Wireshark trace and I see the following happening:

1. The browser does the TLS handshake
2. The browser does a HTTP2 request to the script
3. The server responds with HTTP_1_1_REQUIRED
4. The browser does another request, but now uses HTTP/1.1
5. The server sends a HTTP/1.1 response with the script output

This is most evident when Firefox is used, as it does not remember it should use HTTP/1.1 for the request, where Chrome, Edge and Safari do remember.

Now when I remove the "nph-" prefix from the script name (and do not change the contents), the following happens:

1. The browser does the TLS handshake
2. The browser does a HTTP2 request to the script
3. The server sends the HTTP2 response with the script output

Now I could change all my script names by removing the "nph-" prefix, but it seems that the scripts do not really do NPH anymore as the server is sending back a HTTP2 response, whereas with the "nph-" prefix the exact headers as generated by my script are received by the browser.

Now my question: is it possible to HTTP2 via CGI using the CGI module or any other module?

Marcel