At work, I have set $ENV{HTTP_PROXY} to http://login:password@proxyserver, and it magically works :
use strict;
use WWW::Mechanize;
my $agent = WWW::Mechanize->new();
$agent->env_proxy();
$agent->get('http://www.google.com');
print $agent->content;
perl -MHTTP::Daemon -MHTTP::Response -MLWP::Simple -e ' ; # The
$d = new HTTP::Daemon and fork and getprint $d->url and exit;#spider
($c = $d->accept())->get_request(); $c->send_response( new #in the
HTTP::Response(200,$_,$_,qq(Just another Perl hacker\n))); ' # web