Bite the bullet and apply the hash randomisation patch.

[perl5.git] / pod / perlrun.pod

diff --git a/pod/perlrun.pod b/pod/perlrun.pod
index c33c478..0a02df1 100644 (file)
--- a/pod/perlrun.pod
+++ b/pod/perlrun.pod
@@ -1106,6 +1106,26 @@ references.  See L<perlhack/PERL_DESTRUCT_LEVEL> for more information.
 If using the C<encoding> pragma without an explicit encoding name, the
 PERL_ENCODING environment variable is consulted for an encoding name.
 
+=item PERL_HASH_SEED
+
+(Since Perl 5.8.1.)
+
+Used to randomise Perl's internal hash function.  To emulate the
+pre-5.8.1 behaviour, set to an integer (zero means exactly the same
+order as 5.8.0).  "Pre-5.8.1" means, among other things, that hash
+keys will be ordered the same between different runs of Perl.
+
+The default behaviour is to randomise unless the PERL_HASH_SEED is set.
+If Perl has been compiled with the -DUSE_HASH_SEED_EXPLICIT the default
+behaviour is B<not> to randomise unless the PERL_HASH_SEED is set.
+
+If PERL_HASH_SEED is unset or set to a non-numeric string, Perl uses
+the pseudorandom seed supplied by the operating system and libraries.
+If unset, each different run of Perl will have different ordering of
+the outputs of keys(), values, and each().
+
+See L<perlsec/"Algorithmic Complexity Attacks"> for more information.
+
 =item PERL_ROOT (specific to the VMS port)
 
 A translation concealed rooted logical name that contains perl and the