gistfile1.txt

use v6;

class A {
    has $.a is rw;
    method a is rw {
        Proxy.new(
            FETCH => method () { $!a },
            STORE => method ($v) { $!a = $v }
        );
    }
}

my $o = A.new;
$o.a = 123;
say $o;