Dear Corion,
Thanks for the advice,
I used the following script:

#!/usr/local/bin/perl
use LWP::UserAgent;
use LWP::ConnCache;

my $browser = LWP::UserAgent->new(conn_cache => 1);
$browser->conn_cache(LWP::ConnCache->new());
my @lines = qw(9.9.9.9 8.8.8.8 7.7.7.7 6.6.6.6 5.5.5.5);
my $start = time;
my $url = 'https://xxx.xxx.com/';
my $count = 0;

foreach (@lines) {
    my $response = $browser->get( $url,
                                   'X-Forwarded-For' => $_,
    );
    print $response->as_string;
    $count += length $_;
    sleep(1);
}


print time() - $start;
print " secs\n$count\n";
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