I don't understand how isa fits in here. If you mean to do the following, it seems useless to me. 
package User;

sub find {
    my ($class, $query) = @_;
    die("Bad class") if !$class->isa('User');
    ...
}

[download]

Someone would have to put effort into making that condition fail.

In reply to Re^3: caller package and eval by ikegami
in thread caller package and eval by josh803316

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