$ demo() {
   perl -e'
      use v5.18;
      my %h;
      ++$h{ $_ } for "a".."z";
      say keys %h;
   '
}

$ demo
nylxbvceamuszdrotqfgpwikhj

$ demo
ahedybntzwgmpulqijkrsxfvoc

$ PERL_HASH_SEED=0 demo
udbaxqhcnmskzeiwryvlftojgp

$ PERL_HASH_SEED=0 demo
udbaxqhcnmskzeiwryvlftojgp

$ PERL_HASH_SEED=0x0123456789ABCDEf demo
lfojtgpzekwriyvchmnsuadbqx

$ PERL_HASH_SEED=0x0123456789ABCDEF demo
lfojtgpzekwriyvchmnsuadbqx

##</code><code>##

BEGIN {
   return if exists( $ENV{ PERL_HASH_SEED } );

   $ENV{ PERL_HASH_SEED } = "0";
   exec( $^X, "--", $0, @ARGV )
      or die( "exec: $!" );
}