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1 | =head1 NAME |
2 | ||
4aaa4757 | 3 | CORE - Namespace for Perl's core routines |
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4 | |
5 | =head1 SYNOPSIS | |
6 | ||
1694bc13 RGS |
7 | BEGIN { |
8 | *CORE::GLOBAL::hex = sub { 1; }; | |
9 | } | |
c8472d06 | 10 | |
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11 | print hex("0x50"),"\n"; # prints 1 |
12 | print CORE::hex("0x50"),"\n"; # prints 80 | |
4a904372 | 13 | CORE::say "yes"; # prints yes |
c8472d06 | 14 | |
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15 | BEGIN { *shove = \&CORE::push; } |
16 | shove @array, 1,2,3; # pushes on to @array | |
17 | ||
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18 | =head1 DESCRIPTION |
19 | ||
1694bc13 | 20 | The C<CORE> namespace gives access to the original built-in functions of |
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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 | |
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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 |
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37 | C<shove> example above. These subroutines exist for all keywords except the following: |
38 | ||
39 | C<__DATA__>, C<__END__>, C<and>, C<cmp>, C<default>, C<do>, C<dump>, | |
40 | C<else>, C<elsif>, C<eq>, C<eval>, C<for>, C<foreach>, C<format>, C<ge>, | |
41 | C<given>, C<goto>, C<grep>, C<gt>, C<if>, C<last>, C<le>, C<local>, C<lt>, | |
42 | C<m>, C<map>, C<my>, C<ne>, C<next>, C<no>, C<or>, C<our>, C<package>, | |
43 | C<print>, C<printf>, C<q>, C<qq>, C<qr>, C<qw>, C<qx>, C<redo>, C<require>, | |
44 | C<return>, C<s>, C<say>, C<sort>, C<state>, C<sub>, C<tr>, C<unless>, | |
45 | C<until>, C<use>, C<when>, C<while>, C<x>, C<xor>, C<y> | |
46 | ||
47 | Calling with | |
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48 | ampersand syntax and through references does not work for the following |
49 | functions, as they have special syntax that cannot always be translated | |
50 | into a simple list (e.g., C<eof> vs C<eof()>): | |
51 | ||
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52 | C<chdir>, C<chomp>, C<chop>, C<defined>, C<delete>, C<eof>, C<exec>, |
53 | C<exists>, C<lstat>, C<split>, C<stat>, C<system>, C<truncate>, C<unlink> | |
4aaa4757 | 54 | |
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55 | =head1 OVERRIDING CORE FUNCTIONS |
56 | ||
1694bc13 | 57 | To override a Perl built-in routine with your own version, you need to |
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58 | import it at compile-time. This can be conveniently achieved with the |
59 | C<subs> pragma. This will affect only the package in which you've imported | |
1694bc13 | 60 | the said subroutine: |
c8472d06 | 61 | |
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62 | use subs 'chdir'; |
63 | sub chdir { ... } | |
64 | chdir $somewhere; | |
c8472d06 | 65 | |
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66 | To override a built-in globally (that is, in all namespaces), you need to |
67 | import your function into the C<CORE::GLOBAL> pseudo-namespace at compile | |
68 | time: | |
69 | ||
70 | BEGIN { | |
71 | *CORE::GLOBAL::hex = sub { | |
72 | # ... your code here | |
73 | }; | |
74 | } | |
75 | ||
76 | The new routine will be called whenever a built-in function is called | |
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77 | without a qualifying package: |
78 | ||
1694bc13 | 79 | print hex("0x50"),"\n"; # prints 1 |
c8472d06 | 80 | |
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81 | In both cases, if you want access to the original, unaltered routine, use |
82 | the C<CORE::> prefix: | |
c8472d06 | 83 | |
1694bc13 | 84 | print CORE::hex("0x50"),"\n"; # prints 80 |
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85 | |
86 | =head1 AUTHOR | |
87 | ||
1694bc13 | 88 | This documentation provided by Tels <nospam-abuse@bloodgate.com> 2007. |
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89 | |
90 | =head1 SEE ALSO | |
91 | ||
1694bc13 | 92 | L<perlsub>, L<perlfunc>. |
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93 | |
94 | =cut |