David Coppit (via RT) wrote:
> 
> When running the following script,
> 
>   use Symbol;
> 
>   require Storable;
>   Symbol::delete_package('Storable');
> 
>   # Delete everything just to be safe.
>   map { delete $INC{$_} } keys %INC;
> 
>   require Storable;
>   Storable::freeze([1,2,3]);
> 
> I get the following error:
> 
>   Undefined subroutine &Storable::freeze called at test.pl line 12.
> 
> I was expecting the freeze function to be available after require'ing
> Storable the second time. (i.e. no error)

I will try to explain what I think is happening here with a simpler
example :

Let x.pl contain :

    use Symbol;
    Symbol::delete_package('A');
    require A;
    A::foo();

And A.pm defining a single subroutine :

    package A;
    sub foo {print "foo\n"}
    1;

When x.pl is compiled, the %A:: stash is created to put an empty
placeholder for the foo() subroutine, at compile time. This placeholder
is supposed to be replaced by the actual subroutine when A is loaded (at
runtime, since we use "require A".)

However the placeholder is wiped out by delete_package(), and loading
A.pm recreates a new A stash, but not necessarily with A::foo at the same
memory address. And the original A::foo() call in x.pl has already been
optimized to a glob pointer, since perl is smart enough to avoid a stash
lookup each time it calls a subroutine. This glob has been undefined
by delete_package().

And indeed, changing the A::foo() call to
	&{"A::foo"}();
makes it work, because this forces the symbolic lookup.

I don't know how to fix this.