You're close, but you have to dereference the symbol table entry appropriately, not use it directly as a local variable. The array/hash doesn't get magically created:

use strict;
use warnings;
use feature 'say';

for my $symname (sort keys %main::) {
    local *sym = $main::{$symname};
    say "\@$symname array is populated" if @{ *sym }; # <-- HERE
    say "\%$symname hash  is populated" if %{ *sym }; # <-- and HERE
}

[download]

Output:

%CORE:: hash  is populated
%Carp:: hash  is populated
%DB:: hash  is populated
%DynaLoader:: hash  is populated
%ENV hash  is populated
@INC array is populated
%INC hash  is populated
%IO:: hash  is populated
%Internals:: hash  is populated
%PerlIO:: hash  is populated
%Regexp:: hash  is populated
%Tie:: hash  is populated
%UNIVERSAL:: hash  is populated
%builtin:: hash  is populated
%constant:: hash  is populated
%feature:: hash  is populated
%main:: hash  is populated
%mro:: hash  is populated
%re:: hash  is populated
%strict:: hash  is populated
%utf8:: hash  is populated
%version:: hash  is populated
%warnings:: hash  is populated

[download]

Here's a bit of an example using the actual entries:

use strict;
use warnings;
use feature 'say';

for my $symname (sort keys %main::) {
    local *sym = $main::{$symname};

    # Make a copy of the symtab entry

    if (@{ *sym }) {
        my @array = @{ *sym };
        print "$_\n" for @array;
    }

    # Use the symtab entry directly

    if (%{ *sym }) {
        for my $key (keys %{ *sym }) {
            print "$key: ${ *sym }{$key}\n";
        }
    }
}

[download]

Disclaimer: Please note that using the symbol table directly can be extremely dangerous. You can cause slight or even major problems in very far away code that can be a nightmare or even impossible to track down. This is a very relevant read. It doesn't go into symbol table use directly, but the premise is exactly the same. I find all three parts to be an extremely entertaining and funny read, and it's always nice every couple of years when I have to reference it, as I re-read it each time.

--stevieb

In reply to Re: Interrogating stashes - Camel example doesn't work? by stevieb
in thread Interrogating stashes - Camel example doesn't work? by Intrepid

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