X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperlrun.pod;h=81d47495b755946125c2900cd0fd27c8436dd43a;hb=16114dde8ca7b3eded13218a07f79301ce8c5946;hp=3ddb2f8f682d762e0b7e39304e8f9ab28d078a79;hpb=8229d19fa9e50fd15985d19cead1fb292012b9f9;p=p5sagit%2Fp5-mst-13.2.git

diff --git a/pod/perlrun.pod b/pod/perlrun.pod
index 3ddb2f8..81d4749 100644
--- a/pod/perlrun.pod
+++ b/pod/perlrun.pod
@@ -1139,12 +1139,26 @@ the pseudorandom seed supplied by the operating system and libraries.
 This means that each different run of Perl will have a different
 ordering of the results of keys(), values(), and each().
 
-See L<perlsec/"Algorithmic Complexity Attacks"> for more information.
+B<Please note that the hash seed is sensitive information>. Hashes are
+randomized to protect against local and remote attacks against Perl
+code. By manually setting a seed this protection may be partially or
+completely lost.
+
+See L<perlsec/"Algorithmic Complexity Attacks"> and
+L</PERL_HASH_SEED_DEBUG> for more information.
 
 =item PERL_HASH_SEED_DEBUG
 
-(Since Perl 5.8.1.)  Set to "1" to display (to STDERR) the value of
-the hash seed at the beginning of execution.
+(Since Perl 5.8.1.)  Set to one to display (to STDERR) the value of
+the hash seed at the beginning of execution.  This, combined with
+L</PERL_HASH_SEED> is intended to aid in debugging nondeterministic
+behavior caused by hash randomization.
+
+B<Note that the hash seed is sensitive information>: by knowing it one
+can craft a denial-of-service attack against Perl code, even remotely,
+see L<perlsec/"Algorithmic Complexity Attacks"> for more information.
+B<Do not disclose the hash seed> to people who don't need to know it.
+See also hash_seed() of L<Hash::Util>.
 
 =item PERL_ROOT (specific to the VMS port)