I think that you were on the right track. This worked for me:

use strict;
use warnings;

use HTTP::Proxy;
use HTTP::Recorder;

my $proxy = HTTP::Proxy->new( port => 3128 );

my $agent = new HTTP::Recorder;

#Try C:\Desktop\Agent\log
$agent->file("/home/Desktop/Agent/log");

$proxy->agent( $agent );

$agent->control(["http://127.0.0.1"]);

$proxy->start();

1;
[download]

Try file with one backslash. I added  control. It won't work without it because http://127.0.0.1 will become the URL for my http-recorder.

First, create a directory on the desktop---I called it Agent. Then create a file called log.

Next, after $proxy->start();, minimize the prompt and go to your browser. Manually adjust the browser so that it can use the proxy. Type in http://127.0.0.1, or whatever URL that you want to use. Then start your browsing. After you're finished, check the log in Agent.

I've tried to keep this clear and simple, but if it's not, then please let me know.