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David Golden > perl-5.15.0 > CORE


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Source   Latest Release: perl-5.27.11


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
    CORE::say "yes";                            # prints yes


The CORE namespace gives access to the original built-in functions of Perl. It also provides access to keywords normally available only through the feature pragma. 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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