Thanks for that. It's clear now, and suprising!

It doesn't even matter what package the invocant is blessed into, or even if it's an arbitrary bare word.

use strict;
use warnings FATAL => 'all';

package Base;
sub hello { print __PACKAGE__.": @{[ref $_[0] || $_[0]]}\n"; }

package Kid;
our @ISA = 'Base';

package Main;
sub hello { print __PACKAGE__.": @{[ref $_[0] || $_[0]]}\n"; }

package main;
our @ISA = 'Main';

my $main = bless {};
$main->Kid::hello;    # Base: main
$main->hello;         # Main: main

__PACKAGE__->hello;   # Main: main
BareWord->Kid::hello; # Base: BareWord
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