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

print "$_, $href->{$_}\n" for sort { $href->{$b} <=> $href->{$a} } key
+s %$href;
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If instead of a hash ref you have plain hash, it would change:

my %hash = ( ..... );
print "$_, $hash{$_}\n" for sort { $hash{$b} <=> $hash{$a} } keys %has
+h;
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But the hash construction you demonstrated in your example (despite missing commas) appeared to be the construction of a reference to an anonymous hash.