perl5.git.perl.org Git - perl5.git/blame_incremental

... / ...

Commit	Line	Data
	1	=head1 NAME
	2
	3	CORE - 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
	20	The C<CORE> namespace gives access to the original built-in functions of
	21	Perl. The C<CORE> package is built into
	22	Perl, and therefore you do not need to use or
	23	require a hypothetical "CORE" module prior to accessing routines in this
	24	namespace.
	25
	26	A list of the built-in functions in Perl can be found in L<perlfunc>.
	27
	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
	35	aliases. However, some can only be called as barewords; i.e., you cannot
	36	use ampersand syntax (C<&foo>) or call them through references. See the
	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
	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
	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>
	54
	55	=head1 OVERRIDING CORE FUNCTIONS
	56
	57	To override a Perl built-in routine with your own version, you need to
	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
	60	the said subroutine:
	61
	62	use subs 'chdir';
	63	sub chdir { ... }
	64	chdir $somewhere;
	65
	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
	77	without a qualifying package:
	78
	79	print hex("0x50"),"\n"; # prints 1
	80
	81	In both cases, if you want access to the original, unaltered routine, use
	82	the C<CORE::> prefix:
	83
	84	print CORE::hex("0x50"),"\n"; # prints 80
	85
	86	=head1 AUTHOR
	87
	88	This documentation provided by Tels <nospam-abuse@bloodgate.com> 2007.
	89
	90	=head1 SEE ALSO
	91
	92	L<perlsub>, L<perlfunc>.
	93
	94	=cut