Special variables reserve all slots for their stash symbol i.e. all sigils are globally usable even if only %main:: is meaningful. ( %:: is only the abbreviation)

Compare @a (better @| ) or %0 ¹

(yes its a design flaw)

Btw please start a new thread instead of just changing the title.

edit (7 min)

oops seems like they fixed it for @a

use warnings;
use strict;

%0 = (a=>1);
@| = (1..3);

# @a =(1..3);  #  'requires explicit package name'  if uncommented
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update

see also Scalar followed by parenthetical... and Why did @$ variable bite me in the ass?

And here the reason why @a works as expected

from perlvar:

Perl identifiers that begin with digits, control characters, or punctu
+ation characters are exempt from the effects of the package declarati
+on and are always forced to be in package main ; they are also exempt
+ from strict 'vars' errors. A few other names are also exempt in thes
+e ways:

        ENV      STDIN
        INC      STDOUT
        ARGV     STDERR
        ARGVOUT
        SIG
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