I would look at AnyEvent::HTTP, which allows you to run lots (and lots) of HTTP requests in parallel. To reduce bandwidth on errors, you could first test with a HEAD request and follow up with a GET request on success. If you expect most URLs to be successfull and want the body then, I would just use a GET request.
For grouping all your requests, have a look at the ->begin method of CondVars in AnyEvent.
A rough, untested program could look something like this:
#!perl -w
use strict;
use AnyEvent;
use AnyEvent::HTTP;
my $done = AnyEvent->condvar;
while (my $url = <DATA>) {
$url =~ s!\s+$!!;
$done->begin( sub { $_[0]->send } );
http_get $url, sub {
my ($body, $headers) = @_;
print "Retrieved $url ($headers->{Status})";
$done->end
};
};
print "All requests sent. Waiting for responses.\n";
$done->recv;
print "Done.\n";
__DATA__
http://localhost
http://example.com
http://google.in
Update: Remove whitespace at end of the URLs