my %HoA = ( 
        simpsons    => [ "homer", "marge", "bart" ], 
        flintstones => [ "fred", "barney" ], 
        jetsons     => [ "george", "jane", "elroy", "astro" ], 
); 

my @members= sort map {
    my $key= $_;
    map " $_ : $key", @{$HoA{$key}};
} keys %HoA;

print join $/, @members, "";
__END__

##</code><code>##

 astro : jetsons
 barney : flintstones
 bart : simpsons
 elroy : jetsons
 fred : flintstones
 george : jetsons
 homer : simpsons
 jane : jetsons
 marge : simpsons