FLINTSTONES -- BARNEY, FRED, WILMA
JETSONS -- MAX, TONY, WILMA
SIMPSONS -- LISA, BARNEY, WILMA, HOMER
ALCATRAZ -- ELIJAH, MAX, WILMA

##</code><code>##

my %is_in_show = (
   MAX    => [ 'JETSONS', 'ALCATRAZ' ],
   WILMA  => [ 'FLINTSTONES', 'JETSONS', 'SIMPSONS', 'ALCATRAZ' ],
   HOMER  => [ 'SIMPSONS' ],
   ELIJAH => [ 'ALCATRAZ' ],
   ...
);

##</code><code>##

while (<FILE>) {
   chomp;
   my ($show, $names) = split(/ -- /);
   my @names = split(/, /, $names);
   foreach my $name (@names) {
      push(@{$is_in_show{$name}}, $show);
   }
}

##</code><code>##

use strict;
use warnings;

my %is_in_show;

while (<DATA>) {
   chomp;
   my ($show, $names) = split(/ -- /);
   my @names = split(/, /, $names);
   foreach my $name (@names) {
      push(@{$is_in_show{$name}}, $show);
   }
}

foreach my $name (keys %is_in_show) {
   my $shows = $is_in_show{$name};
   my $num_shows = @$shows;
   my $s = $num_shows == 1 ? '' : 's';
   print("$name appears in $num_shows show$s: ",
         join(' ', @$shows), "\n");
}

__DATA__
FLINTSTONES -- BARNEY, FRED, WILMA
JETSONS -- MAX, TONY, WILMA
SIMPSONS -- LISA, BARNEY, WILMA, HOMER
ALCATRAZ -- ELIJAH, MAX, WILMA