This is a naff suggestion - I don't have the env to test it..., but it should be easy for you to try...

sub html_1 {
  printnow("your stuff is being processed");
}

sub html_2{
  printnow("your process is done");
  
}

# 8K cache buster...
sub printnow {
  print @_, "<br>", " " x 8192, \n",;
}
[download]

It assumes that you are using Apache, and that it has the usual 8K bucket cacheing.

So I don't really propose that you use it, but it may illustrate that the problem with immediate user feedback is in fact, Apache 8K cache.

An alternate solution is to have an IFRAME in your code, and fetch the start page into the IFRAME, and then on some reasonable timed basis, fetch a progress / completion page. This is pretty easy for Javascript on most modern browsers.

Regards, Jeff