| =head1 NAME |
| |
| CORE - Namespace for Perl's core routines |
| |
| =head1 SYNOPSIS |
| |
| BEGIN { |
| *CORE::GLOBAL::hex = sub { 1; }; |
| } |
| |
| print hex("0x50"),"\n"; # prints 1 |
| print CORE::hex("0x50"),"\n"; # prints 80 |
| CORE::say "yes"; # prints yes |
| |
| BEGIN { *shove = \&CORE::push; } |
| shove @array, 1,2,3; # pushes on to @array |
| |
| =head1 DESCRIPTION |
| |
| The C<CORE> namespace gives access to the original built-in functions of |
| Perl. The C<CORE> package is built into |
| Perl, and therefore you do not need to use or |
| require a hypothetical "CORE" module prior to accessing routines in this |
| namespace. |
| |
| A list of the built-in functions in Perl can be found in L<perlfunc>. |
| |
| For all Perl keywords, a C<CORE::> prefix will force the built-in function |
| to be used, even if it has been overridden or would normally require the |
| L<feature> pragma. Despite appearances, this has nothing to do with the |
| CORE package, but is part of Perl's syntax. |
| |
| For many Perl functions, the CORE package contains real subroutines. This |
| feature is new in Perl 5.16. You can take references to these and make |
| aliases. However, some can only be called as barewords; i.e., you cannot |
| use ampersand syntax (C<&foo>) or call them through references. See the |
| C<shove> example above. These subroutines exist for all overridable |
| keywords, except for C<dump> and the infix operators. Calling with |
| ampersand syntax and through references does not work for the following |
| functions, as they have special syntax that cannot always be translated |
| into a simple list (e.g., C<eof> vs C<eof()>): |
| |
| C<chdir>, C<chomp>, C<chop>, C<each>, C<eof>, C<exec>, C<keys>, C<lstat>, |
| C<pop>, C<push>, C<shift>, C<splice>, C<stat>, C<system>, C<truncate>, |
| C<unlink>, C<unshift>, C<values> |
| |
| =head1 OVERRIDING CORE FUNCTIONS |
| |
| To override a Perl built-in routine with your own version, you need to |
| import it at compile-time. This can be conveniently achieved with the |
| C<subs> pragma. This will affect only the package in which you've imported |
| the said subroutine: |
| |
| use subs 'chdir'; |
| sub chdir { ... } |
| chdir $somewhere; |
| |
| To override a built-in globally (that is, in all namespaces), you need to |
| import your function into the C<CORE::GLOBAL> pseudo-namespace at compile |
| time: |
| |
| BEGIN { |
| *CORE::GLOBAL::hex = sub { |
| # ... your code here |
| }; |
| } |
| |
| The new routine will be called whenever a built-in function is called |
| without a qualifying package: |
| |
| print hex("0x50"),"\n"; # prints 1 |
| |
| In both cases, if you want access to the original, unaltered routine, use |
| the C<CORE::> prefix: |
| |
| print CORE::hex("0x50"),"\n"; # prints 80 |
| |
| =head1 AUTHOR |
| |
| This documentation provided by Tels <nospam-abuse@bloodgate.com> 2007. |
| |
| =head1 SEE ALSO |
| |
| L<perlsub>, L<perlfunc>. |
| |
| =cut |