[] does not do what you think it does in a regexp. I would do a sub to do what you want done.

# Zone 8 
my $z8 = "10-374,376-379,382-385,388-499,530-534,541-543,618,619,700-7
+04,707-709";

my $num = "375";
print "Found it!\n" if in_range($z8, $num); #$num =~/[$z8]/;

sub in_range{
    my $numbers = shift;
    my $num = shift;

    my @ranges = split ',', $numbers;

    foreach my $r (@ranges){
        if (my ($small, $big) = $r =~ /^(\d+)-(\d+)$/){
            return 1 if $small <= $num and $big >= $num;
        }
        elsif( my ($n) = $r =~ /^(\d+)$/){
            return 1 if $n == $num;
        }
        else{
            die 'Oh noo:-(';
        }
    }
    return 0;
}
[download]

Update: Fixed bugs