local $SIG {ALRM} = sub {die "alarm"};
my $fh;

eval {
    alarm (2);
    open $fh, "-|", "$vmdiscover ..." or die "Couldn't open $vmdiscover: $!";
    while (<$fh>) {};
    alarm (0);
};
if ($@ && $@ =~ /^alarm/) {
    print "Command has timed out";
}
elsif ($@) {
    print "$@\n";
}
close $fh;