Commit | Line | Data |
---|---|---|
c8472d06 T |
1 | =head1 NAME |
2 | ||
4aaa4757 | 3 | CORE - Namespace for Perl's core routines |
c8472d06 T |
4 | |
5 | =head1 SYNOPSIS | |
6 | ||
1694bc13 RGS |
7 | BEGIN { |
8 | *CORE::GLOBAL::hex = sub { 1; }; | |
9 | } | |
c8472d06 | 10 | |
1694bc13 RGS |
11 | print hex("0x50"),"\n"; # prints 1 |
12 | print CORE::hex("0x50"),"\n"; # prints 80 | |
4a904372 | 13 | CORE::say "yes"; # prints yes |
c8472d06 | 14 | |
4aaa4757 FC |
15 | BEGIN { *shove = \&CORE::push; } |
16 | shove @array, 1,2,3; # pushes on to @array | |
17 | ||
c8472d06 T |
18 | =head1 DESCRIPTION |
19 | ||
1694bc13 | 20 | The C<CORE> namespace gives access to the original built-in functions of |
4aaa4757 FC |
21 | Perl. The C<CORE> package is built into |
22 | Perl, and therefore you do not need to use or | |
5840c18f | 23 | require a hypothetical "CORE" module prior to accessing routines in this |
1694bc13 | 24 | namespace. |
c8472d06 | 25 | |
1694bc13 | 26 | A list of the built-in functions in Perl can be found in L<perlfunc>. |
c8472d06 | 27 | |
4aaa4757 FC |
28 | For all Perl keywords, a C<CORE::> prefix will force the built-in function |
29 | to be used, even if it has been overridden or would normally require the | |
30 | L<feature> pragma. Despite appearances, this has nothing to do with the | |
31 | CORE package, but is part of Perl's syntax. | |
32 | ||
33 | For many Perl functions, the CORE package contains real subroutines. This | |
34 | feature is new in Perl 5.16. You can take references to these and make | |
2702a50a | 35 | aliases. However, some can only be called as barewords; i.e., you cannot |
4aaa4757 | 36 | use ampersand syntax (C<&foo>) or call them through references. See the |
d47dcd9c FC |
37 | C<shove> example above. These subroutines exist for all overridable |
38 | keywords, except for C<dump> and the infix operators. Calling with | |
2702a50a FC |
39 | ampersand syntax and through references does not work for the following |
40 | functions, as they have special syntax that cannot always be translated | |
41 | into a simple list (e.g., C<eof> vs C<eof()>): | |
42 | ||
43 | C<chdir>, C<chomp>, C<chop>, C<each>, C<eof>, C<exec>, C<keys>, C<lstat>, | |
44 | C<pop>, C<push>, C<shift>, C<splice>, C<stat>, C<system>, C<truncate>, | |
45 | C<unlink>, C<unshift>, C<values> | |
4aaa4757 | 46 | |
c8472d06 T |
47 | =head1 OVERRIDING CORE FUNCTIONS |
48 | ||
1694bc13 RGS |
49 | To override a Perl built-in routine with your own version, you need to |
50 | import it at compile-time. This can be conveniently achieved with the | |
51 | C<subs> pragma. This will affect only the package in which you've imported | |
52 | the said subroutine: | |
c8472d06 | 53 | |
1694bc13 RGS |
54 | use subs 'chdir'; |
55 | sub chdir { ... } | |
56 | chdir $somewhere; | |
c8472d06 | 57 | |
1694bc13 RGS |
58 | To override a built-in globally (that is, in all namespaces), you need to |
59 | import your function into the C<CORE::GLOBAL> pseudo-namespace at compile | |
60 | time: | |
61 | ||
62 | BEGIN { | |
63 | *CORE::GLOBAL::hex = sub { | |
64 | # ... your code here | |
65 | }; | |
66 | } | |
67 | ||
68 | The new routine will be called whenever a built-in function is called | |
c8472d06 T |
69 | without a qualifying package: |
70 | ||
1694bc13 | 71 | print hex("0x50"),"\n"; # prints 1 |
c8472d06 | 72 | |
1694bc13 RGS |
73 | In both cases, if you want access to the original, unaltered routine, use |
74 | the C<CORE::> prefix: | |
c8472d06 | 75 | |
1694bc13 | 76 | print CORE::hex("0x50"),"\n"; # prints 80 |
c8472d06 T |
77 | |
78 | =head1 AUTHOR | |
79 | ||
1694bc13 | 80 | This documentation provided by Tels <nospam-abuse@bloodgate.com> 2007. |
c8472d06 T |
81 | |
82 | =head1 SEE ALSO | |
83 | ||
1694bc13 | 84 | L<perlsub>, L<perlfunc>. |
c8472d06 T |
85 | |
86 | =cut |