=over 8
+=item $a
+
+=item $b
+
+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.
+
+=back
+
+=over 8
+
=item $<I<digits>>
Contains the subpattern from the corresponding set of capturing
=item $*
-Set to 1 to do multi-line matching within a string, 0 to tell Perl
-that it can assume that strings contain a single line, for the purpose
-of optimizing pattern matches. Pattern matches on strings containing
-multiple newlines can produce confusing results when C<$*> is 0. Default
-is 0. (Mnemonic: * matches multiple things.) This variable
-influences the interpretation of only C<^> and C<$>. A literal newline can
-be searched for even when C<$* == 0>.
+Set to a non-zero integer value to do multi-line matching within a
+string, 0 (or undefined) to tell Perl that it can assume that strings
+contain a single line, for the purpose of optimizing pattern matches.
+Pattern matches on strings containing multiple newlines can produce
+confusing results when C<$*> is 0 or undefined. Default is undefined.
+(Mnemonic: * matches multiple things.) This variable influences the
+interpretation of only C<^> and C<$>. A literal newline can be searched
+for even when C<$* == 0>.
Use of C<$*> is deprecated in modern Perl, supplanted by
the C</s> and C</m> modifiers on pattern matching.
+Assigning a non-numerical value to C<$*> triggers a warning (and makes
+C<$*> act if C<$* == 0>), while assigning a numerical value to C<$*>
+makes that an implicit C<int> is applied on the value.
+
=item input_line_number HANDLE EXPR
=item $INPUT_LINE_NUMBER
=item $<
The real uid of this process. (Mnemonic: it's the uid you came I<from>,
-if you're running setuid.)
+if you're running setuid.) You can change both the real uid and
+the effective uid at the same time by using POSIX::setuid().
=item $EFFECTIVE_USER_ID
$< = $>; # set real to effective uid
($<,$>) = ($>,$<); # swap real and effective uid
+You can change both the effective uid and the real uid at the same
+time by using POSIX::setuid().
+
(Mnemonic: it's the uid you went I<to>, if you're running setuid.)
C<< $< >> and C<< $> >> can be swapped only on machines
supporting setreuid().
set the real gid. So the value given by C<$(> 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().
+
(Mnemonic: parentheses are used to I<group> things. The real gid is the
group you I<left>, if you're running setgid.)
to force an effective gid of 5 and an effectively empty setgroups()
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).
+
(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.)
would allocate a 64K buffer for use in an emergency. See the
F<INSTALL> file in the Perl distribution for information on how to
enable this option. To discourage casual use of this advanced
-feature, there is no L<English> long name for this variable.
+feature, there is no L<English|English> long name for this variable.
=item $OSNAME
script is in the right range of versions. (Mnemonic: use ^V for Version
Control.) Example:
- warn "No "our" declarations!\n" if $^V and $^V lt v5.6.0;
+ warn "No \"our\" declarations!\n" if $^V and $^V lt v5.6.0;
See the documentation of C<use VERSION> and C<require VERSION>
for a convenient way to fail if the running Perl interpreter is too old.
one, because C<$ARGV[0]> is the first argument, I<not> the program's
command name itself. See C<$0> for the command name.
+=item @F
+
+The array @F contains the fields of each line read in when autosplit
+mode is turned on. See L<perlrun> for the B<-a> switch. This array
+is package-specific, and must be declared or given a full package name
+if not in package main when running under C<strict 'vars'>.
+
=item @INC
The array @INC contains the list of places that the C<do EXPR>,