wait what?

wtf.pl

#!/usr/bin/perl -w

use strict;
use warnings;

{
    package DEEP;
    sub deeply { "deeply inherited" }

    package UNIVERSAL;
    our @ISA = qw/DEEP/;

    package Foo;
    our @ISA = qw//;
}

print "Foo can do deeply\n" if Foo->can('deeply');
print "Foo isa UNIVERSAL\n" if Foo->isa('UNIVERSAL');
print "Foo is, strangely, not DEEP\n" unless Foo->isa('DEEP');