my %hash = ( a=>0, b=>1, c=>0, d=>3 );
foreach my $k ( sort { $hash{$a} <=> $hash{$b} or $a cmp $b } keys %hash  ) {
    print "$k = $hash{$k}\n";
}

##</code><code>##

a = 0
c = 0
b = 1
d = 3