Perl 5 version 14.2 documentation



CORE - Pseudo-namespace for Perl's core routines


  1. BEGIN {
  2. *CORE::GLOBAL::hex = sub { 1; };
  3. }
  4. print hex("0x50"),"\n"; # prints 1
  5. print CORE::hex("0x50"),"\n"; # prints 80


The CORE namespace gives access to the original built-in functions of Perl. There is no CORE package, and therefore you do not need to use or require an hypothetical "CORE" module prior to accessing routines in this namespace.

A list of the built-in functions in Perl can be found in perlfunc.


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 subs pragma. This will affect only the package in which you've imported the said subroutine:

  1. use subs 'chdir';
  2. sub chdir { ... }
  3. chdir $somewhere;

To override a built-in globally (that is, in all namespaces), you need to import your function into the CORE::GLOBAL pseudo-namespace at compile time:

  1. BEGIN {
  2. *CORE::GLOBAL::hex = sub {
  3. # ... your code here
  4. };
  5. }

The new routine will be called whenever a built-in function is called without a qualifying package:

  1. print hex("0x50"),"\n"; # prints 1

In both cases, if you want access to the original, unaltered routine, use the CORE:: prefix:

  1. print CORE::hex("0x50"),"\n"; # prints 80


This documentation provided by Tels <> 2007.


perlsub, perlfunc.