FWIW, I changed the regex to

my $page = ($req =~ m/^(?:GET|POST|HEAD)\s*(.*?)\s/)[0];
[download]

And (assuming this works:), I am posting this reply via your proxy.

As far as the IO::Socket::INET code is concerned, as far as I can tell, it should be ok. The module is being replicated into each thread, so each will have its own copy of the code and as the underlying resource is a GLOB, essentially a filehandle, it is a process global resource that should work okay so long as you don't try and use it simultaneously.

I *think* that by locking $browser inside the if statement in process_one_req(), before you print to it, you should be okay to stick with it.... I'll try to verify this.