Generation of a HASH OF COMPLEX RECORDS

     # reading from file
     # this is most easily done by having the file itself be
     # in the raw data format as shown above.  perl is happy
     # to parse complex data structures if declared as data, so
     # sometimes it's easiest to do that

     # here's a piece by piece build up
     $rec = {};
     $rec->{series} = "flintstones";
     $rec->{nights} = [ find_days() ];

     @members = ();
     # assume this file in field=value syntax
     while (<>) {
         %fields = split /[\s=]+/;
         push @members, { %fields };
     }
     $rec->{members} = [ @members ];

     # now remember the whole thing
     $TV{ $rec->{series} } = $rec;

     ###########################################################
     # now, you might want to make interesting extra fields that
     # include pointers back into the same data structure so if
     # change one piece, it changes everywhere, like for examples
     # if you wanted a {kids} field that was an array reference
     # to a list of the kids' records without having duplicate
     # records and thus update problems.
     ###########################################################
     foreach $family (keys %TV) {
         $rec = $TV{$family}; # temp pointer
         @kids = ();
         for $person ( @{ $rec->{members} } ) {
             if ($person->{role} =~ /kid|son|daughter/) {
                 push @kids, $person;
             }
         }
         # REMEMBER: $rec and $TV{$family} point to same data!!
         $rec->{kids} = [ @kids ];
     }

     # you copied the list, but the list itself contains pointers
     # to uncopied objects. this means that if you make bart get
     # older via

     $TV{simpsons}{kids}[0]{age}++;

     # then this would also change in
     print $TV{simpsons}{members}[2]{age};

     # because $TV{simpsons}{kids}[0] and $TV{simpsons}{members}[2]
     # both point to the same underlying anonymous hash table

     # print the whole thing
     foreach $family ( keys %TV ) {
         print "the $family";
         print " is on during @{ $TV{$family}{nights} }\n";
         print "its members are:\n";
         for $who ( @{ $TV{$family}{members} } ) {
             print " $who->{name} ($who->{role}), age $who->{age}\n";
         }
         print "it turns out that $TV{$family}{lead} has ";
         print scalar ( @{ $TV{$family}{kids} } ), " kids named ";
         print join (", ", map { $_->{name} } @{ $TV{$family}{kids} } );
         print "\n";
     }