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t/perlvar.pod  view on Meta::CPAN

	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

t/perlvaro.txt  view on Meta::CPAN

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 ...
This behavior provides the semantic of lexical scoping, and is used in, for instance, the 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 co...
Substitution of the above BEGIN block with:
    BEGIN { require strict; strict->import('vars') }
demonstrates how use strict 'vars' is implemented. Here's a conditional version of the same lexical pragma:
    BEGIN { require strict; strict->import('vars') if $condition }
%^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.
$INPLACE_EDIT
$^I
The current value of the inplace-edit extension. Use undef to disable inplace editing. (Mnemonic: value of -i switch.)
$^M
By default, running out of memory is an untrappable, fatal error. However, if suitably built, Perl can use the contents of $^M as an emergency memory pool after die()ing. Suppose that your Perl were compiled with -DPERL_EMERGENCY_SBRK and used Perl's...
    $^M = 'a' x (1 << 16);
would allocate a 64K buffer for use in an emergency. See the 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 English long name for this variable.