Try reordering. This won't be a problem if you put Person in its own module, as you might do when creating a larger program:

{
    package Person;
    use Class::Std;

    my %name_of : ATTR(init_arg => 'name',  get => 'name', set => 'nam
+e');
}

package main;

my $guy = Person->new({name => 'Bubba'});
print "name: ", $guy->get_name, "\n";

$guy->set_name('Gump');
print "name: ", $guy->get_name, "\n";
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(My reformattings make no difference; I just prefer them for clarity and separation.)