What the Anonymous Monk is referring to is doing this in your code:

use LWP;
require LWP::Protocol::http10;
LWP::Protocol::implementor('http', 'LWP::Protocol::http10');

my $ua = LWP::UserAgent->new();
$ua->get('http://server.local/foo');
[download]

This code would connect to server.local using HTTP/1.0 instead of HTTP/1.1.

But instead of using LWP::Protocol::http10 as your Protocol implementor, copy LWP::Protocol::http10 code to a new module, perhaps call it MyLWP::Protocol::brokenhttp and change the code in there to use your custom HTTP version and GET format

Update: This was slightly covered already, but something like: find the LWP/Protocol/http10.pm file in your perl library, copy it to your local lib path as MyLWP/Protocol/brokenhttp.pm then edit it, then use that name as the last option to the implementor function.