my ($sec,$min,$hour) = qw( 0 0 12 );
my ($mday, $mon, $year) = qw(11 5 2007);
$mon--; # because that's how unix/C treat the month value

eval {
    my $dummy = timelocal($sec,$min,$hour,$mday,$mon,$year);
};
if (my $err = $@) {
    print "This is an invalid date.";
} else {
    print "Yay";
};