ithreads: cond_signal() on a non-shared object coredumped

[perl5.git] / pod / perlvar.pod

diff --git a/pod/perlvar.pod b/pod/perlvar.pod
index 72cb625..292f444 100644 (file)
--- a/pod/perlvar.pod
+++ b/pod/perlvar.pod
@@ -177,6 +177,11 @@ test.  Outside a C<while> test, this will not happen.
 
 =back
 
+As C<$_> is a global variable, this may lead in some cases to unwanted
+side-effects.  As of perl 5.9.1, you can now use a lexical version of
+C<$_> by declaring it in a file or in a block with C<my>.  Moreover,
+declaring C<our $> restores the global C<$_> in the current scope.
+
 (Mnemonic: underline is understood in certain operations.)
 
 =back
@@ -189,10 +194,9 @@ test.  Outside a C<while> test, this will not happen.
 
 Special package variables when using sort(), see L<perlfunc/sort>.
 Because of this specialness $a and $b don't need to be declared
-(using local(), use vars, or our()) even when using the strict
-vars pragma.  Don't lexicalize them with C<my $a> or C<my $b>
-if you want to be able to use them in the sort() comparison block
-or function.
+(using use vars, or our()) even when using the C<strict 'vars'> pragma.
+Don't lexicalize them with C<my $a> or C<my $b> if you want to be
+able to use them in the sort() comparison block or function.
 
 =back
 
@@ -471,8 +475,6 @@ taken for something more important.)
 Consider using "real" multidimensional arrays as described
 in L<perllol>.
 
-=item $OFMT
-
 =item $#
 
 The output format for printed numbers.  This variable is a half-hearted
@@ -675,7 +677,7 @@ In the above I<meaningless> stands for anything: zero, non-zero,
 C<undef>.  A successful system or library call does B<not> set
 the variable to zero.
 
-If used an a string, yields the corresponding system error string.
+If used as a string, yields the corresponding system error string.
 You can assign a number to C<$!> to set I<errno> if, for instance,
 you want C<"$!"> to return the string for error I<n>, or you want
 to set the exit value for the die() operator.  (Mnemonic: What just
@@ -763,7 +765,9 @@ you may use the CPAN module C<Linux::Pid>.
 
 The real uid of this process.  (Mnemonic: it's the uid you came I<from>,
 if you're running setuid.)  You can change both the real uid and
-the effective uid at the same time by using POSIX::setuid().
+the effective uid at the same time by using POSIX::setuid().  Since
+changes to $< require a system call, check $! after a change attempt to 
+detect any possible errors.
 
 =item $EFFECTIVE_USER_ID
 
@@ -777,7 +781,8 @@ The effective uid of this process.  Example:
     ($<,$>) = ($>,$<); # swap real and effective uid
 
 You can change both the effective uid and the real uid at the same
-time by using POSIX::setuid().
+time by using POSIX::setuid().  Changes to $> require a check to $!
+to detect any possible errors after an attempted change. 
 
 (Mnemonic: it's the uid you went I<to>, if you're running setuid.)
 C<< $< >> and C<< $> >> can be swapped only on machines
@@ -800,7 +805,8 @@ set the real gid.  So the value given by C<$(> should I<not> be assigned
 back to C<$(> without being forced numeric, such as by adding zero.
 
 You can change both the real gid and the effective gid at the same
-time by using POSIX::setgid().
+time by using POSIX::setgid().  Changes to $( require a check to $!
+to detect any possible errors after an attempted change.
 
 (Mnemonic: parentheses are used to I<group> things.  The real gid is the
 group you I<left>, if you're running setgid.)
@@ -826,6 +832,8 @@ list, say C< $) = "5 5" >.
 
 You can change both the effective gid and the real gid at the same
 time by using POSIX::setgid() (use only a single numeric argument).
+Changes to $) require a check to $! to detect any possible errors
+after an attempted change.
 
 (Mnemonic: parentheses are used to I<group> things.  The effective gid
 is the group that's I<right> for you, if you're running setgid.)