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Rafaël Garcia-Suarez > perl-5.10.0 > CORE


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Source   Latest Release: perl-5.28.0-RC3


CORE - Pseudo-namespace for Perl's core routines


    BEGIN {
        *CORE::GLOBAL::hex = sub { 1; };

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

    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 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 CORE:: prefix:

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


This documentation provided by Tels <> 2007.


perlsub, perlfunc.

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