PerlFAQ sync.

p4raw-id: //depot/perl@23509

1 files changed, 8 insertions, 12 deletions

diff --git a/pod/perlfaq4.pod b/pod/perlfaq4.pod
index 0e62c2b436..815a9ea428 100644
--- a/pod/perlfaq4.pod
+++ b/pod/perlfaq4.pod
@@ -1,6 +1,6 @@
 =head1 NAME
 
-perlfaq4 - Data Manipulation ($Revision: 1.55 $, $Date: 2004/10/11 05:06:29 $)
+perlfaq4 - Data Manipulation ($Revision: 1.56 $, $Date: 2004/11/03 22:47:56 $)
 
 =head1 DESCRIPTION
 
@@ -1715,19 +1715,15 @@ sorting the keys as shown in an earlier question.
 
 =head2 What happens if I add or remove keys from a hash while iterating over it?
 
-Don't do that. :-)
+(contributed by brian d foy)
 
-[lwall] In Perl 4, you were not allowed to modify a hash at all while
-iterating over it.  In Perl 5 you can delete from it, but you still
-can't add to it, because that might cause a doubling of the hash table,
-in which half the entries get copied up to the new top half of the
-table, at which point you've totally bamboozled the iterator code.
-Even if the table doesn't double, there's no telling whether your new
-entry will be inserted before or after the current iterator position.
+The easy answer is "Don't do that!"
 
-Either treasure up your changes and make them after the iterator finishes
-or use keys to fetch all the old keys at once, and iterate over the list
-of keys.
+If you iterate through the hash with each(), you can delete the key
+most recently returned without worrying about it.  If you delete or add
+other keys, the iterator may skip or double up on them since perl
+may rearrange the hash table.  See the
+entry for C<each()> in L<perlfunc>.
 
 =head2 How do I look up a hash element by value?