use strict;
use warnings;

use B;

package Foo;

sub thing {}

my $ref1 = \&package1::sub1;
my $ref2 = \&thing;

package Bar;

for ($ref1, $ref2) {
    print B::svref_2object($_)->STASH->NAME, "\n";
    print B::svref_2object($_)->GV->STASH->NAME, "\n";
}

# Output:
#   main
#   package1
#   Foo
#   Foo
[download]

Apparently $cv->STASH->NAME is always "main" if the reference was constructed via an absolute name (like $ref1 was).