#   iterate by sorted list of hash keys
foreach my $key (sort keys %hash) {
    ...
}

#    iterate by sorted list of hash values
foreach my $key (sort { $hash{$b} <=> $hash{$a} } keys %hash) {
    ...
}

##</code><code>##

#   iterate by reverse sorted list of hash keys
foreach my $key (reverse sort keys %hash) {
    ...
}

#    iterate by reverse sorted list of hash values
foreach my $key (reverse sort { $hash{$b} <=> $hash{$a} } keys %hash) {
    ...
}