http://www.perlmonks.org?node_id=942184


in reply to Config::Config{osname} and Config{osname}

%Config::Config like @Config::ISA lives in package Config; while %Config lives in package main;

When you use Config; it exports %Config into your current package (main). If you use package Huang; use Config; it exports (creates) %Config in package Huang; The fully qualified name of this exported (created) %Config is %Huang::Config;

It is a global variable.

This "exporting" is a copy. Copies take memory. So if you use Config(); or require Config; no copy gets made in your current namespace, but you can still access the original by its full name %Config::Config;

Read Tutorials: Variable Scoping in Perl: the basics, Coping with Scoping

Replies are listed 'Best First'.
Re^2: Config::Config{osname} and Config{osname}
by Anonymous Monk on Dec 07, 2011 at 09:14 UTC

    This "exporting" is a copy. Copies take memory.

    Actually, it only copies a reference, not a lot of memory 

    perl -MConfig -le " print \%Config::Config; print \%Config; "
HASH(0x99abe4)
HASH(0x99abe4)

    [download]
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Re^2: Config::Config{osname} and Config{osname}
by PhillipHuang (Beadle) on Dec 07, 2011 at 09:43 UTC
    I see. When 'use Config' first, and then in 'package Huang', it must be identified with original path as "$Config::Config". If use '$Config{osname}', it will warn 'Global symbol "%Config" requires explicit package'.
[reply]

      Yup, it all depends what package you're in 

      $ perl -l
use strict; use warnings;
use Config; # main
package Huang;
use Config;
package Batman;
use Config;
package main;
print \%Config; 
print \%Huang::Config;
print \%Batman::Config;
print \%main::Config;
print \%Config::Config;
__END__
HASH(0x99abcc)
HASH(0x99abcc)
HASH(0x99abcc)
HASH(0x99abcc)
HASH(0x99abcc)

      [download]
[reply]
[d/l]

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