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CORE(3perl) - phpMan

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CORE(3perl)                      Perl Programmers Reference Guide                     CORE(3perl)

       CORE - 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

           BEGIN { *shove = \&CORE::push; }
           shove @array, 1,2,3;                        # pushes on to @array

       The "CORE" namespace gives access to the original built-in functions of Perl.  The "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 perlfunc.

       For all Perl keywords, a "CORE::" prefix will force the built-in function to be used, even
       if it has been overridden or would normally require the 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 (&foo) or call them through
       references.  See the "shove" example above.  These subroutines exist for all keywords
       except the following:

       "__DATA__", "__END__", "and", "cmp", "default", "do", "dump", "else", "elsif", "eq",
       "eval", "for", "foreach", "format", "ge", "given", "goto", "grep", "gt", "if", "last",
       "le", "local", "lt", "m", "map", "my", "ne", "next", "no", "or", "our", "package",
       "print", "printf", "q", "qq", "qr", "qw", "qx", "redo", "require", "return", "s", "say",
       "sort", "state", "sub", "tr", "unless", "until", "use", "when", "while", "x", "xor", "y"

       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., "eof" vs "eof()"):

       "chdir", "chomp", "chop", "defined", "delete", "each", "eof", "exec", "exists", "keys",
       "lstat", "pop", "push", "shift", "splice", "split", "stat", "system", "truncate",
       "unlink", "unshift", "values"

       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

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

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

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

       This documentation provided by Tels <nospam-abuse AT bloodgate.com> 2007.

       perlsub, perlfunc.

perl v5.20.2                                2014-12-27                                CORE(3perl)

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