my $href = {
  env4 => 20140830,
  env1 => 20140829,
  env2 => 20140828,
  env3 => 20140828,
};

print "$_, $href->{$_}\n" for sort { $href->{$b} <=> $href->{$a} } keys %$href;


##</code><code>##

my %hash = ( ..... );
print "$_, $hash{$_}\n" for sort { $hash{$b} <=> $hash{$a} } keys %hash;