Looking at the source, I don't see anything that cares when mk_accessors is called. I also don't have any problems as desired.

package KLARF;

use strict;
use warnings;

use Class::Accessor qw( );

our @ISA = 'Class::Accessor';

__PACKAGE__->mk_accessors(qw( foo ));

sub more {
    __PACKAGE__->mk_accessors(qw( bar ));
}

1;
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$ perl -wle'
    use KLARF;
    KLARF::more();
    my $o = KLARF->new();
    $o->foo("abc"); print $o->foo();
    $o->bar("def"); print $o->bar();
'
abc
def
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By the way, using __PACKAGE__ is usually deemed wiser than hardcoding the package name everywhere.