I can't really see, how "die" in your code could produce any output. It is called by ALRM signal handler inside of eval, so the output of "die" is saved in $@ and not printed anywhere. If you get some output, then it comes from somewhere else. Check for example this code

my $ch;

eval{
    $SIG{ALRM} = sub{
        die "Waiting finished\n";
    };
    alarm(10);
    $ch = <STDIN>;
    alarm(0);
};

if($@)
{
    print "Timeout happened\n";
}
else
{
    print "Got $ch";
}
[download]

You'll never see "Waiting finished" because it is stored in $@ variable and the code does not print it.