1=head1 NAME 2 3CORE - Namespace for Perl's core routines 4 5=head1 SYNOPSIS 6 7 BEGIN { 8 *CORE::GLOBAL::hex = sub { 1; }; 9 } 10 11 print hex("0x50"),"\n"; # prints 1 12 print CORE::hex("0x50"),"\n"; # prints 80 13 CORE::say "yes"; # prints yes 14 15 BEGIN { *shove = \&CORE::push; } 16 shove @array, 1,2,3; # pushes on to @array 17 18=head1 DESCRIPTION 19 20The C<CORE> namespace gives access to the original built-in functions of 21Perl. The C<CORE> package is built into 22Perl, and therefore you do not need to use or 23require a hypothetical "CORE" module prior to accessing routines in this 24namespace. 25 26A list of the built-in functions in Perl can be found in L<perlfunc>. 27 28For all Perl keywords, a C<CORE::> prefix will force the built-in function 29to be used, even if it has been overridden or would normally require the 30L<feature> pragma. Despite appearances, this has nothing to do with the 31CORE package, but is part of Perl's syntax. 32 33For many Perl functions, the CORE package contains real subroutines. This 34feature is new in Perl 5.16. You can take references to these and make 35aliases. However, some can only be called as barewords; i.e., you cannot 36use ampersand syntax (C<&foo>) or call them through references. See the 37C<shove> example above. These subroutines exist for all keywords except the following: 38 39C<__DATA__>, C<__END__>, C<and>, C<cmp>, C<default>, C<do>, C<dump>, 40C<else>, C<elsif>, C<eq>, C<eval>, C<for>, C<foreach>, C<format>, C<ge>, 41C<given>, C<goto>, C<grep>, C<gt>, C<if>, C<last>, C<le>, C<local>, C<lt>, 42C<m>, C<map>, C<my>, C<ne>, C<next>, C<no>, C<or>, C<our>, C<package>, 43C<print>, C<printf>, C<q>, C<qq>, C<qr>, C<qw>, C<qx>, C<redo>, C<require>, 44C<return>, C<s>, C<say>, C<sort>, C<state>, C<sub>, C<tr>, C<unless>, 45C<until>, C<use>, C<when>, C<while>, C<x>, C<xor>, C<y> 46 47Calling with 48ampersand syntax and through references does not work for the following 49functions, as they have special syntax that cannot always be translated 50into a simple list (e.g., C<eof> vs C<eof()>): 51 52C<chdir>, C<chomp>, C<chop>, C<defined>, C<delete>, C<eof>, C<exec>, 53C<exists>, C<lstat>, C<split>, C<stat>, C<system>, C<truncate>, C<unlink> 54 55=head1 OVERRIDING CORE FUNCTIONS 56 57To override a Perl built-in routine with your own version, you need to 58import it at compile-time. This can be conveniently achieved with the 59C<subs> pragma. This will affect only the package in which you've imported 60the said subroutine: 61 62 use subs 'chdir'; 63 sub chdir { ... } 64 chdir $somewhere; 65 66To override a built-in globally (that is, in all namespaces), you need to 67import your function into the C<CORE::GLOBAL> pseudo-namespace at compile 68time: 69 70 BEGIN { 71 *CORE::GLOBAL::hex = sub { 72 # ... your code here 73 }; 74 } 75 76The new routine will be called whenever a built-in function is called 77without a qualifying package: 78 79 print hex("0x50"),"\n"; # prints 1 80 81In both cases, if you want access to the original, unaltered routine, use 82the C<CORE::> prefix: 83 84 print CORE::hex("0x50"),"\n"; # prints 80 85 86=head1 AUTHOR 87 88This documentation provided by Tels <nospam-abuse@bloodgate.com> 2007. 89 90=head1 SEE ALSO 91 92L<perlsub>, L<perlfunc>. 93 94=cut 95