These are perfectly valid Ruby code, and evaluate to nil, nil, and a lambda.[].inject( :-)
{}[ :-]
->() { :-}
Of course, the nose is easily substitutable, and noseless ones can use any mouth they please... but what about changing the eyes, or the mouth on full-size ones, and additional adornments? Let's see how creative you can get, especially in as few characters as possible on either side. Put some new Rubymoticons in the comments.