Directly remove an entry from the symbol table

johnnywang has asked for the wisdom of the Perl Monks concerning the following question:

This is a follow up on the discussion in keys %::. Since the "package Foo;" statement introduces an entry in the main symbol table $::{'Foo::'} as well as its typeglobed value %Foo::, it seems that if I delete this entry explicitly, then one should not be able to do "Foo->new()", and the Foo symbol table should be gone also. The following code confirms the first, but it seems the %Foo:: still exists, why is that?

# test.pl
use strict;

package Foo;

sub new{
    return bless {}, shift;
}

sub foo{
    my $self = shift;
    print "Foo called\n";
}

package main;

# print the full symbol table, notice the Foo:: entry
print "$_ => $::{$_}\n" foreach keys %::;
print "\n\n";

delete $::{'Foo::'}; # shouldn't this delete the symbol table for Foo?

# print again the full symbol table, notice Foo:: is gone.
print "$_ => $::{$_}\n" foreach keys %::;
print "\n\n";

# seems still there.
print "$_ => $Foo::{$_}\n" foreach keys %Foo::; 
print "\n\n";

# but can't call the following, as expected
my $f = new Foo(); 
$f->foo();
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On cywin, the result is (removed some entries to make it shorter):

" => *main::"
CORE:: => *main::CORE::
strict:: => *main::strict::
$ => *main::$
Foo:: => *main::Foo::
main:: => *main::main::
 => *main::
@ => *main::@
<none>:: => *main::<none>::

" => *main::"
CORE:: => *main::CORE::
strict:: => *main::strict::
$ => *main::$
main:: => *main::main::
 => *main::
@ => *main::@
<none>:: => *main::<none>::

foo => *Foo::foo
new => *Foo::new

Can't locate object method "new" via package "Foo" (perhaps you forgot
+ to load "
Foo"?) at test.pl line 30.
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Re: Directly remove an entry from the symbol table
by tlm (Prior) on May 03, 2005 at 11:41 UTC

FWIW, if you replace the last two lines of your script with

my $f = $Foo::{'new'}->( 'Foo' );
$Foo::{'foo'}->( $f );
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Foo

main

Foo

the lowliest monk

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Re: Directly remove an entry from the symbol table
by PodMaster (Abbot) on May 03, 2005 at 06:13 UTC

my $z = new Foo::();
$z->foo();
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MJD says "you can't just make shit up and expect the computer to know what you mean, retardo!"
I run a Win32 PPM repository for perl 5.6.x and 5.8.x -- I take requests (README).
** The third rule of perl club is a statement of fact: pod is sexy.

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Re: Directly remove an entry from the symbol table
by osunderdog (Deacon) on May 03, 2005 at 14:44 UTC

Have you looked at:

use Symbol qw|delete_package|;

Here's the chunk I used:

  eval
  {
    delete_package($packageName);
    # Have to remove the package from the %INC hash so that require wi
+ll
    # actually load the package again.
    delete($INC{$packageFile});  
  };
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I can't say that I ever got package dropping to work 100%. It doesn't free up memory for the package.

Hope this helps.

Soon to be unemployed!

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