perl symbol table

The contents of a package are collectively called a symbol table. Symbol tables are stored in a hash whose name is the same as the package, but with two colons

appended. The main symbol table’s name is thus %main::. Since main also happens to be the default package, Perl provides %:: as an abbreviation for %main::.

以上引自<Programming Perl 4th>

当创建package variables 时，Perl会在对应的symbol tables(%package::)中创建对应的一个typeglob项。

code:

#!/usr/bin/perl -l


use strict;
use warnings;
{our $var = "Hello World";}    #注意此处用的是our, 因为my 声明的变量会存到symbol tables中
sub var{print "in sub var()"};


foreach (keys %main::){
        print $_ . "==>" .$main::{$_};
}


print "Done";
print "#" x 80;
print ${*var{SCALAR}};
&{*var{CODE}}();

======================================================================================================================

/==>*main::/
stderr==>*main::stderr
SIG==>*main::SIG
utf8::==>*main::utf8::
"==>*main::"
ARNING_BITS==>*main::ARNING_BITS
CORE::==>*main::CORE::
DynaLoader::==>*main::DynaLoader::
strict::==>*main::strict::
stdout==>*main::stdout
attributes::==>*main::attributes::
==>*main::
stdin==>*main::stdin
ARGV==>*main::ARGV
INC==>*main::INC
ENV==>*main::ENV
Regexp::==>*main::Regexp::
UNIVERSAL::==>*main::UNIVERSAL::
$==>*main::$
_<perlio.c==>*main::_<perlio.c
main::==>*main::main::
Carp::==>*main::Carp::
-==>*main::-
_<perlmain.c==>*main::_<perlmain.c
PerlIO::==>*main::PerlIO::
_<universal.c==>*main::_<universal.c
0==>*main::0
var==>*main::var      #此处极为的symbol table中的对应项
BEGIN==>*main::BEGIN                                                                                                                                                   ==>*main::
@==>*main::@
_<xsutils.c==>*main::_<xsutils.c
!==>*main::!
STDOUT==>*main::STDOUT
IO::==>*main::IO::
==>*main::
_==>*main::_
+==>*main::+
Exporter::==>*main::Exporter::
STDERR==>*main::STDERR
Internals::==>*main::Internals::
STDIN==>*main::STDIN
warnings::==>*main::warnings::
DB::==>*main::DB::
<none>::==>*main::<none>::
Done
################################################################################
Hello World
in sub var()