Warnings when sorting by hashref

[Mike Martin]

Hi

I have the following code as an example against a hash of hashes, to sort
by hashrf key

foreach my $opt (sort {uc($options{$b}->{type}) cmp
uc($options{$a}->{type})} keys %options){
            my $type=$options{$opt}->{vtype};
                $video_type->append_text($type) if defined($type) ;
                }

The sort function works perfectly, however perl throws up the following
warning for each line

Use of uninitialized value in uc at

Any ideas how to get rid of the warning

thanks

Mike