$ perl -V  | grep SEED
    PERL_HASH_SEED="-1"

##</code><code>##

#!/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";

##</code><code>##

$ 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