typo fix

[p5sagit/p5-mst-13.2.git] / pod / perlvar.pod

diff --git a/pod/perlvar.pod b/pod/perlvar.pod
index 9402608..a43ab60 100644 (file)
--- a/pod/perlvar.pod
+++ b/pod/perlvar.pod
@@ -45,9 +45,7 @@ you try to assign to this variable, either directly or indirectly through
 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
 
@@ -272,7 +270,7 @@ set, you'll get the record back in pieces.
 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.
 
@@ -719,8 +717,54 @@ C<$^F> when the open() or pipe() was called, not the time of the exec().
 
 =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
 
@@ -816,7 +860,12 @@ and B<-C> filetests are based on this value.
 
 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
 
@@ -861,7 +910,7 @@ The hash %INC contains entries for each filename included via the
 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
@@ -965,7 +1014,7 @@ Carp was available.  The third line will be executed only if Carp was
 not available.
 
 See L<perlfunc/die>, L<perlfunc/warn>, L<perlfunc/eval>, and
-L<warning> for additional information.
+L<warnings> for additional information.
 
 =back
 
@@ -1040,7 +1089,7 @@ C<W>) is the scalar variable whose name is the single character
 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