There are a number of ways to handle getting the retrieved data back to the parent or other process that don't require use of shared memory:

• use MLDBM::Sync
• use Cache::Cache (specifically Cache::FileCache)
• use database that runs as a daemon (e.g. MySQL or PostgresQL).

As it turns out, HTTP::MHTTP seems to have an 'issue' with name-based virtual hosts, exhibited by the code below, so I can't use that, and it doesn't appear to work on Windows machines either, which puts it in the non-portable category for me:

   use strict;
   use HTTP::MHTTP;

   # This url REALLY exists, but is a virtual host 
   # on a domain shared by multiple hosts.
   my $url = 'http://advogato.org/recentlog.html;

   http_init();
   switch_debug(1);
   http_call("GET", $url);
   print http_response();
[download]

Thanks to bart and ChemBoy for the enlightening discussion that exposed this issue.

Based on my loose testing (excluding HTTP::MHTTP), it looks like HTTP::GHTTP is the fastest, followed closely by HTTP::Lite and LWP::Simple behind that. I haven't done benching against Parallel::ForkManager yet with these, so that waits to be seen.

The other issue also, is the speed at which DNS queries are resolved. I think I can speed that up with a local database of resolved sites, but on the first run, that'll take a hit.

Thanks for the tips and hints though, I'm closer to a functional solution, but it seems the more I test, the farther down the stack I get, closer to writing my own code around IO::Socket. I'd like to avoid that if I can.