a reference, you'll raise a run-time exception.
The following list is ordered by scalar variables first, then the
-arrays, then the hashes (except $^M was added in the wrong place).
-This is somewhat obscured because %ENV and %SIG are listed as
-$ENV{expr} and $SIG{expr}.
+arrays, then the hashes.
=over 8
On VMS, record reads are done with the equivalent of C<sysread>,
so it's best not to mix record and non-record reads on the same
file. (This is unlikely to be a problem, because any file you'd
-want to read in record mode is probably usable in line mode.)
+want to read in record mode is probably unusable in line mode.)
Non-VMS systems do normal I/O, so it's safe to mix record and
non-record reads of a file.
See also the documentation of C<use VERSION> and C<require VERSION>
for a convenient way to fail if the running Perl interpreter is too old.
+See C<$^V> for a more modern representation of the Perl version.
+
=item $COMPILING
=item $^C
=item $^H
-The current set of syntax checks enabled by C<use strict> and other block
-scoped compiler hints. See the documentation of C<strict> for more details.
+WARNING: This variable is strictly for internal use only. Its availability,
+behavior, and contents are subject to change without notice.
+
+This variable contains compile-time hints for the Perl interpreter. At the
+end of compilation of a BLOCK the value of this variable is restored to the
+value when the interpreter started to compile the BLOCK.
+
+When perl begins to parse any block construct that provides a lexical scope
+(e.g., eval body, required file, subroutine body, loop body, or conditional
+block), the existing value of $^H is saved, but its value is left unchanged.
+When the compilation of the block is completed, it regains the saved value.
+Between the points where its value is saved and restored, code that
+executes within BEGIN blocks is free to change the value of $^H.
+
+This behavior provides the semantic of lexical scoping, and is used in,
+for instance, the C<use strict> pragma.
+
+The contents should be an integer; different bits of it are used for
+different pragmatic flags. Here's an example:
+
+ sub add_100 { $^H |= 0x100 }
+
+ sub foo {
+ BEGIN { add_100() }
+ bar->baz($boon);
+ }
+
+Consider what happens during execution of the BEGIN block. At this point
+the BEGIN block has already been compiled, but the body of foo() is still
+being compiled. The new value of $^H will therefore be visible only while
+the body of foo() is being compiled.
+
+Substitution of the above BEGIN block with:
+
+ BEGIN { require strict; strict->import('vars') }
+
+demonstrates how C<use strict 'vars'> is implemented. Here's a conditional
+version of the same lexical pragma:
+
+ BEGIN { require strict; strict->import('vars') if $condition }
+
+=item %^H
+
+WARNING: This variable is strictly for internal use only. Its availability,
+behavior, and contents are subject to change without notice.
+
+The %^H hash provides the same scoping semantic as $^H. This makes it
+useful for implementation of lexically scoped pragmas.
=item $INPLACE_EDIT
Start with single-step on.
+=item 0x40
+
+Use subroutine address instead of name when reporting.
+
+=item 0x80
+
+Report C<goto &subroutine> as well.
+
+=item 0x100
+
+Provide informative "file" names for evals based on the place they were compiled.
+
+=item 0x200
+
+Provide informative names to anonymous subroutines based on the place they
+were compiled.
+
=back
Some bits may be relevant at compile-time only, some at
epoch (beginning of 1970). The values returned by the B<-M>, B<-A>,
and B<-C> filetests are based on this value.
+=item $^U
+
+Global flag that switches on Unicode character support in the Perl
+interpreter. The initial value is usually C<0> for compatibility
+with Perl versions earlier than 5.6, but may be automatically set
+to C<1> by Perl if the system provides a user-settable default
+(e.g., C<$ENV{LC_CTYPE}>). It is also implicitly set to C<1>
+whenever the utf8 pragma is loaded.
+
+Setting it to C<1> has the following effects:
+
+=over
+
+=item *
+
+C<chr> produces UTF-8 encoded Unicode characters. These are the same
+as the corresponding ASCII characters if the argument is less than 128.
+
+=item *
+
+The C<%c> format in C<sprintf> generates a UTF-8 encoded Unicode
+character. This is the same as the corresponding ASCII character
+if the argument is less than 128.
+
+=item *
+
+Any system calls made by Perl will use wide character APIs native to
+the system, if available. This is currently only implemented on the
+Windows platform.
+
+=back
+
+The C<byte> pragma overrides the value of this flag in the current
+lexical scope. See L<byte>.
+
+=item $^V
+
+The revision, version, and subversion of the Perl interpreter, represented
+as a "version tuple". Version tuples have both a numeric value and a
+string value. The numeric value is a floating point number that amounts
+to revision + version/1000 + subversion/1000000, and the string value
+is made of utf8 characters:
+C<chr($revision) . chr($version) . chr($subversion)>.
+
+This can be used to determine whether the Perl interpreter executing a
+script is in the right range of versions. (Mnemonic: use ^V for Version
+control.) Example:
+
+ warn "No "our" declarations!\n" if $^V and $^V lt v5.6;
+
+See also the documentation of C<use VERSION> and C<require VERSION>
+for a convenient way to fail if the running Perl interpreter is too old.
+
+See also C<$]> for an older representation of the Perl version.
+
=item $WARNING
=item $^W
The current value of the warning switch, initially true if B<-w>
was used, false otherwise, but directly modifiable. (Mnemonic:
-related to the B<-w> switch.) See also L<warning>.
+related to the B<-w> switch.) See also L<warnings>.
+
+=item ${^Warnings}
+
+The current set of warning checks enabled by the C<use warnings> pragma.
+See the documentation of C<warnings> for more details.
=item $EXECUTABLE_NAME
C<do>, C<require>, or C<use> operators. The key is the filename
you specified (with module names converted to pathnames), and the
value is the location of the file found. The C<require>
-operator uses this array to determine whether a particular file has
+operator uses this hash to determine whether a particular file has
already been included.
=item %ENV
not available.
See L<perlfunc/die>, L<perlfunc/warn>, L<perlfunc/eval>, and
-L<warning> for additional information.
+L<warnings> for additional information.
=back
control-C<W>. This is better than typing a literal control-C<W>
into your program.
-Finally, new in Perl 5.006, Perl variable names may be alphanumeric
+Finally, new in Perl 5.6, Perl variable names may be alphanumeric
strings that begin with control characters (or better yet, a caret).
These variables must be written in the form C<${^Foo}>; the braces
are not optional. C<${^Foo}> denotes the scalar variable whose
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