I'm trying to add a handler for LWPUserAgent, this handler must to choose UserAgent string for each request and choose and to choose a proxy for this request, but something is going wrong, makerequest subroutine isn't applied to requests. Thanks in advance.

Script:

my (@agents,@routes);
open( AGENTS, "<", "/etc/agents.cfg" );
        while( <AGENTS> ) {
        s/#.*//;
        next if /^(\s)*$/;
        chomp;
        push @agents, $_;
}
close(AGENTS);

open( ROUTES, "<", "/etc/routes.cfg" );
        while( <ROUTES> ) {
        s/#.*//;
        next if /^(\s)*$/;
        chomp;
        push @routes, $_;
}
close(ROUTES);

my $ua = LWP::UserAgent->new();

sub cb {
        my($request, $ua, $h) = @_;
        my $i = $#agents + 1;
        $i = rand($i);
        $i = int $i;

        my $j = $#routes + 1;
        $j = rand($j);
        $j = int $j; 



        my $cur_agent = $agents[$i];
        my $cur_proxy = $routes[$j]; 
        $request->header($cur_agent);
        $ua->timeout(10);
        $ua->proxy(['http'],$cur_proxy);

}

$ua->add_handler( request_prepare => \&cb);
....
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