use strict; use warnings; use feature 'say';
use LWP::UserAgent;

my $foo = 'bar';
$SIG{'INT'} = sub {
    $foo = 'baz';
};

my $ua = LWP::UserAgent->new;
$ua->add_handler("response_data", sub {
    if ( $foo eq 'baz' ) {
        say 'killing UA now';
        croak();
    }
    return 1;
});

my $url = 'http://ipv4.download.thinkbroadband.com/10MB.zip';
my $filename = "$0.zip";

my $forked = fork // die 'Could not fork!';
if ( $forked == 0 ) { # child
    say "In child with $$";
    my $req = HTTP::Request->new( GET => $url );
    my $res = $ua->request( $req, $filename );
    exit;
}

my $done = wait;

say "In parent: $done done";

exit;