blah.hat=splat
cat=doh,ray

##</code><code>##

...
my $Config = {
    some => 'default values',
};
while (<CONFIG>) {
    chomp;
    my ($key, $value) = split /=/,2;
    my @path = split /\./, $key;
    my $loc = $Config;
    my $last = pop @path;
    for (@path) {
        $loc->{$_} ||= {};
        $loc = $loc->{$_};
    };
    if ($value =~ /,/) { # Store an array
        $loc->{$last} = [ split /,/, $value ];
    } else {
        $loc->{$last} = $value;
    };
};