On p5p, where this is already being discussed, Rick Delaney presented a simpler snippet that demonstrates the problem.

package F;
sub foo { "foo" }
       
package G; @ISA = qw(F);
print \&foo; # creates entry in G's symbol table

package main;
my $o = bless [],"G";
print $o->foo;
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CODE(0x8149624)
Undefined subroutine &G::foo called at - line 9.
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I'm not sure why perl-diddler didn't post this much more readable snippet...