More docs and tests for "my $_".

p4raw-id: //depot/perl@22265

2 files changed, 12 insertions, 0 deletions

diff --git a/pod/perlfunc.pod b/pod/perlfunc.pod
index a7bbacc9fc..13cfdab3c8 100644
--- a/pod/perlfunc.pod
+++ b/pod/perlfunc.pod
@@ -2230,6 +2230,11 @@ element of a list returned by grep (for example, in a C<foreach>, C<map>
 or another C<grep>) actually modifies the element in the original list.
 This is usually something to be avoided when writing clear code.
 
+If C<$_> is lexical in the scope where the C<grep> appears (because it has
+been declared with C<my $_>) then, in addition the be locally aliased to
+the list elements, C<$_> keeps being lexical inside the block; i.e. it
+can't be seen from the outside, avoiding any potential side-effects.
+
 See also L</map> for a list composed of the results of the BLOCK or EXPR.
 
 =item hex EXPR
@@ -2615,6 +2620,11 @@ Using a regular C<foreach> loop for this purpose would be clearer in
 most cases.  See also L</grep> for an array composed of those items of
 the original list for which the BLOCK or EXPR evaluates to true.
 
+If C<$_> is lexical in the scope where the C<map> appears (because it has
+been declared with C<my $_>) then, in addition the be locally aliased to
+the list elements, C<$_> keeps being lexical inside the block; i.e. it
+can't be seen from the outside, avoiding any potential side-effects.
+
 C<{> starts both hash references and blocks, so C<map { ...> could be either
 the start of map BLOCK LIST or map EXPR, LIST. Because perl doesn't look
 ahead for the closing C<}> it has to take a guess at which its dealing with
diff --git a/pod/perlsub.pod b/pod/perlsub.pod
index 969d0ba039..e830130a55 100644
--- a/pod/perlsub.pod
+++ b/pod/perlsub.pod
@@ -588,6 +588,8 @@ separator.
 Notably, if you want to work with a brand new value of the default scalar
 $_, and avoid the potential problem listed above about $_ previously
 carrying a magic value, you should use C<local *_> instead of C<local $_>.
+As of perl 5.9.1, you can also use the lexical form of C<$_> (declaring it
+with C<my $_>), which avoids completely this problem.
 
 =head3 Localization of elements of composite types