The C<*foo{THING}> notation can also be used to obtain references to the
individual elements of *foo, see L<perlref>.
+Subroutine definitions (and declarations, for that matter) need
+not necessarily be situated in the package whose symbol table they
+occupy. You can define a subroutine outside its package by
+explicitly qualifying the name of the subroutine:
+
+ package main;
+ sub Some_package::foo { ... } # &foo defined in Some_package
+
+This is just a shorthand for a typeglob assignment at compile time:
+
+ BEGIN { *Some_package::foo = sub { ... } }
+
+and is I<not> the same as writing:
+
+ {
+ package Some_package;
+ sub foo { ... }
+ }
+
+In the first two versions, the body of the subroutine is
+lexically in the main package, I<not> in Some_package. So
+something like this:
+
+ package main;
+
+ $Some_package::name = "fred";
+ $main::name = "barney";
+
+ sub Some_package::foo {
+ print "in ", __PACKAGE__, ": \$name is '$name'\n";
+ }
+
+ Some_package::foo();
+
+prints:
+
+ in main: $name is 'barney'
+
+rather than:
+
+ in Some_package: $name is 'fred'
+
+This also has implications for the use of the SUPER:: qualifier
+(see L<perlobj>).
+
=head2 Package Constructors and Destructors
-There are two special subroutine definitions that function as package
-constructors and destructors. These are the C<BEGIN>, C<INIT>, and
-C<END> routines. The C<sub> is optional for these routines.
+Four special subroutines act as package constructors and destructors.
+These are the C<BEGIN>, C<CHECK>, C<INIT>, and C<END> routines. The
+C<sub> is optional for these routines.
A C<BEGIN> subroutine is executed as soon as possible, that is, the moment
it is completely defined, even before the rest of the containing file
has run, it is immediately undefined and any code it used is returned to
Perl's memory pool. This means you can't ever explicitly call a C<BEGIN>.
-An C<END> subroutine is executed as late as possible, that is, when
-the interpreter is being exited, even if it is exiting as a result of
-a die() function. (But not if it's polymorphing into another program
-via C<exec>, or being blown out of the water by a signal--you have to
-trap that yourself (if you can).) You may have multiple C<END> blocks
-within a file--they will execute in reverse order of definition; that is:
-last in, first out (LIFO).
+An C<END> subroutine is executed as late as possible, that is, after
+perl has finished running the program and just before the interpreter
+is being exited, even if it is exiting as a result of a die() function.
+(But not if it's polymorphing into another program via C<exec>, or
+being blown out of the water by a signal--you have to trap that yourself
+(if you can).) You may have multiple C<END> blocks within a file--they
+will execute in reverse order of definition; that is: last in, first
+out (LIFO). C<END> blocks are not executed when you run perl with the
+C<-c> switch.
Inside an C<END> subroutine, C<$?> contains the value that the program is
going to pass to C<exit()>. You can modify C<$?> to change the exit
value of the program. Beware of changing C<$?> by accident (e.g. by
running something via C<system>).
+Similar to C<BEGIN> blocks, C<INIT> blocks are run just before the
+Perl runtime begins execution, in "first in, first out" (FIFO) order.
+For example, the code generators documented in L<perlcc> make use of
+C<INIT> blocks to initialize and resolve pointers to XSUBs.
+
+Similar to C<END> blocks, C<CHECK> blocks are run just after the
+Perl compile phase ends and before the run time begins, in
+LIFO order. C<CHECK> blocks are again useful in the Perl compiler
+suite to save the compiled state of the program.
+
When you use the B<-n> and B<-p> switches to Perl, C<BEGIN> and
C<END> work just as they do in B<awk>, as a degenerate case. As currently
implemented (and subject to change, since its inconvenient at best),
both C<BEGIN> and<END> blocks are run when you use the B<-c> switch
for a compile-only syntax check, although your main code is not.
-Similar to C<BEGIN> blocks, C<INIT> blocks are run just before the
-Perl runtime begins execution. For example, the code generators
-documented in L<perlcc> make use of C<INIT> blocks to initialize
-and resolve pointers to XSUBs.
-
=head2 Perl Classes
There is no special class syntax in Perl, but a package may act
BEGIN {
use Exporter ();
- use vars qw($VERSION @ISA @EXPORT @EXPORT_OK %EXPORT_TAGS);
+ our ($VERSION, @ISA, @EXPORT, @EXPORT_OK, %EXPORT_TAGS);
# set the version for version checking
$VERSION = 1.00;
# as well as any optionally exported functions
@EXPORT_OK = qw($Var1 %Hashit &func3);
}
- use vars @EXPORT_OK;
+ our @EXPORT_OK;
# non-exported package globals go here
- use vars qw(@more $stuff);
+ our @more;
+ our $stuff;
# initialize package globals, first exported ones
$Var1 = '';
projects / p5sagit/p5-mst-13.2.git / blobdiff