Sorry, I wrote it as a getter, not an accessor.

handles => {
    this => sub { @_ == 1
        ? $_[0]->data->{this}
        : $_[0]->data->{this} = $_[1] },
    that => sub { @_ == 1
        ? $_[0]->data->{that}
        : $_[0]->data->{that} = $_[1] },
},
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You can use a map to avoid duplication and/or an accessor generating function.