Is there anything I can do?

Yes, you can detect the broken browser, and inform the user to get a better one (see HTTP::BrowserDetect).

I'd like the script to work with the majority of browsers...

It already does. The majority of browsers correctly implement the HTTP/CGI protocols, and as such, work. Only these can be called browsers. The others, like Safari, are broken-browsers, so they have no hope of working.