Personally I would go for something more like this:

    STDIN | /\w+/ | {|each match|
      /house/   => "foo"
      /car/     => "bar"
      "literal" => "baz"
      _         => "dib"
    }

Where "each x" in a parameter list wraps the body in a map and uses x as the loop variable, and "match" in a parameter list instructs that this is the parameter we are doing pattern matching on in the body (no need to name it).

I think this is a more flexible solution, and more modifiers than each could be introduced. For instance, sum of squares could be:

    seq(100) | {|each x| x * x} | {|reduce (x = 0, y)| x + y}