}
[..normal %ENV behavior here..]
+It's also worth taking a moment to explain what happens when you
+localize a member of a composite type (i.e. an array or hash element).
+In this case, the element is localized I<by name>. This means that
+when the scope of the C<local()> ends, the saved value will be
+restored to the hash element whose key was named in the C<local()>, or
+the array element whose index was named in the C<local()>. If that
+element was deleted while the C<local()> was in effect (e.g. by a
+C<delete()> from a hash or a C<shift()> of an array), it will spring
+back into existence, possibly extending an array and filling in the
+skipped elements with C<undef>. For instance, if you say
+
+ %hash = ( 'This' => 'is', 'a' => 'test' );
+ @ary = ( 0..5 );
+ {
+ local($ary[5]) = 6;
+ local($hash{'a'}) = 'drill';
+ while (my $e = pop(@ary)) {
+ print "$e . . .\n";
+ last unless $e > 3;
+ }
+ if (@ary) {
+ $hash{'only a'} = 'test';
+ delete $hash{'a'};
+ }
+ }
+ print join(' ', map { "$_ $hash{$_}" } sort keys %hash),".\n";
+ print "The array has ",scalar(@ary)," elements: ",
+ join(', ', map { defined $_ ? $_ : 'undef' } @ary),"\n";
+
+Perl will print
+
+ 6 . . .
+ 4 . . .
+ 3 . . .
+ This is a test only a test.
+ The array has 6 elements: 0, 1, 2, undef, undef, 5
+
+In short, be careful when manipulating the containers for composite types
+whose elements have been localized.
=head2 Passing Symbol Table Entries (typeglobs)
chdir $somewhere;
sub chdir { ... }
+To unambiguously refer to the builtin form, one may precede the
+builtin name with the special package qualifier C<CORE::>. For example,
+saying C<CORE::open()> will always refer to the builtin C<open()>, even
+if the current package has imported some other subroutine called
+C<&open()> from elsewhere.
+
Library modules should not in general export builtin names like "open"
or "chdir" as part of their default @EXPORT list, because these may
sneak into someone else's namespace and change the semantics unexpectedly.
they would get the default imports without the overrides.
+Note that such overriding is restricted to the package that requests
+the import. Some means of "globally" overriding builtins may become
+available in future.
+
=head2 Autoloading
If you call a subroutine that is undefined, you would ordinarily get an