my $cmd = ...;

    my $pid;
    my $fh;
    my @out;
    eval {
        local $SIG{ALRM} = sub { die "Timeout\n" };
        alarm 5;
        $pid = open($fh, '-|', $cmd)
           or die;
        @out = <$fh>;
        undef $fh;
        alarm 0;
    };
    kill TERM => $pid if defined($fh);