# features (source): {'pos' => '^(([^N].).*\\Z|(N).*\\@(.).*\\Z)/$2$3$4'}
# features (target): {'pos' => '^(..).*$/$1'}
# features (source): {'pos' => '^(([^N].).*\\Z|(N).*\\@(.).*\\Z)/$2$3$4'}
# features (target): {'pos' => '^(..).*$/$1'}