How does perl know how to find $Yakkity::Yak::a after the package's symbol table is gone?

Perl uses an internal type called a typeglob to hold an entire symbol table entry. The type prefix of a typeglob is a *, because it represents all types.

What you quoted is not relevant. What you quoted describes a symbol table entry, so it has no bearing on whether %Yakkity::Yak:: is a symbol table or not.

Except that it is relevant. The symbol table for the Yakkity::Yak namespace is found in *Yakkity::Yak::.

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.

How does perl know how to find $Yakkity::Yak::a after the package's symbol table is gone?

Dave.

To illustrate dave_the_m's and Bob9000's point, compare

#!/usr/bin/perl
$Yakkity::Yak::a = 42;
print "a = $Yakkity::Yak::a\n";
print "Undeffing symbol table\n";
undef %Yakkity::Yak::;
print "a = $Yakkity::Yak::a\n";
__END__
a = 42
Undeffing symbol table
a = 42
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with

#!/usr/bin/perl
$Yakkity::Yak::a = 42;
print "a = $Yakkity::Yak::a\n";
print "Undeffing symbol table\n";
undef %Yakkity::Yak::;
print "a = ${'Yakkity::Yak::a'}\n";  # <- Hardcoded reference removed
__END__
a = 42
Undeffing symbol table
a =
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The last reference to $Yakkity::Yak::a keeps the symbol alive. If the reference to one built at run-time, the symbol disappears along with the table.

Sorry, this post just explains what is seen, not how to work around it. Hopefully, someone has a solution.

It doesn't. However, it seems to compile $Yakkity::Yak::a as a hard reference to a specific entry in the symbol table, allowing that glob and the variables it references to continue existing after it has been removed from the table. Notice that after undeffing the symbol table, attempting to access the variable with a soft reference (i.e. ${"Yakkity::Yak::a"}), or with a direct reference in any code compiled later (i.e. eval '$Yakkity::Yak::a'), will fail...although compiling the new code (or accessing a soft reference) will create another variable named $Yakkity::Yak::a, which is unrelated to the one referenced by code compiled before the undeffing.

Looking back at this post, I probably should have stopped after two sentences. But then, I had a little too much fun playing with this not to make a few notes.

Suppose I were creating dynamic packages at runtime and I want to make sure all the stuff in them gets destroyed. How would I ensure that?

use Symbol 'delete_package';
use Data::Dumper;

$Yakkity::Yak::a = 42;

print "a = $Yakkity::Yak::a\n";
print Dumper \%Yakkity::Yak::;

print "Undeffing symbol table\n";
delete_package 'Yakkity::Yak';

print "a = $Yakkity::Yak::a\n";
print Dumper \%Yakkity::Yak::;

__output__

a = 42
$VAR1 = {
          'a' => *Yakkity::Yak::a
        };
Undeffing symbol table
a = 
$VAR1 = {};
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