for (sort keys %hash) {
    print "$_ => ";

    if (ref($hash{$_}) eq 'ARRAY') {
        print join(', ', @{ $hash{$_} });
    }
    elsif (ref($hash{$_}) eq 'HASH') {
        # do something else
    }
    else {
        print $hash{$_};
    }

    print "\n";
}