Since Perl 5.8.1 the ordering is different even between different runs of Perl for security reasons (see "Algorithmic Complexity Attacks" in perlsec)."

I just wonder if Red Hat didn't turn the randomization off on purpose in the name of compatibility to make sure that older applications didn't break when keys started to come back randomly. I have no doc that says that's the case, that just seems reasonable to me. Here's the option to do it:

From perlrun:

The default behaviour is to randomise unless the PERL_HASH_SEED is set. If Perl has been compiled with -DUSE_HASH_SEED_EXPLICIT, the default behaviour is not to randomise unless the PERL_HASH_SEED is set.

Actually I've checked output for perl -V :

$ perl -V  | grep SEED
    PERL_HASH_SEED="-1"
[download]

But setting the PERL_HASH_SEED env variable has no effect at all. Using this script :

#!/usr/bin/perl
use strict;
use warnings;
use Hash::Util qw(hash_seed);

my %t=qw( a A b B c C d D e E f F );

print hash_seed() . "\n";

print join( '', %t) ."\n";
[download]

I change the PERL_HASH_SEED, the hash_seed differs from run to run, but the hash order remains the same:

$ for i in -1 0 1 42 garbage; do export PERL_HASH_SEED=$i; for j in 1 
+2 3; do perl test.pl; done; done
3657515954
eEcCaAbBdDfF
3070542819
eEcCaAbBdDfF
185686570
eEcCaAbBdDfF
0
eEcCaAbBdDfF
0
eEcCaAbBdDfF
0
eEcCaAbBdDfF
1
eEcCaAbBdDfF
1
eEcCaAbBdDfF
1
eEcCaAbBdDfF
42
eEcCaAbBdDfF
42
eEcCaAbBdDfF
42
eEcCaAbBdDfF
3381895560
eEcCaAbBdDfF
2632524130
eEcCaAbBdDfF
1729561246
eEcCaAbBdDfF
[download]

The hash seed has no effect, that sucks!