0x0dea

Subtle.

    Person = Struct.new :name, :age

    people = [
      Person.new('Alice', 42),
      Person.new('Bob',   23),
      Person.new('Carol', 30)
    ]

    people.sort_by(&:age).map(&:name)
    # => ["Bob", "Carol", "Alice"]

    $ whatis code
    code: nothing appropriate.

No, it can't. If this is something you've seen "many times", would you mind providing an example? Show me a program that Ruby tries to execute without having been able to parse it.