The Hpricot library allows the following syntax:

Hpricot(my_document)

This is not idiomatic Ruby, and a novice programmer might not know what it did, or how. UrbanHonking explains how, but James Robertson takes issue over why.

If you are going to bend a language's idiomatic usage, you should have a compelling reason, and I share James' view that this example is not compelling.

But other examples are compelling. In Ruby, I could say this:

class Person < ActiveRecord::Base
  has_many = ["opinions"]
  validates_presence_of("first_name")
end

Yuck. Better:

class Person < ActiveRecord::Base
  has_many :opinions
  validates_presence_of :first_name
end

That's how it would look in Rails today. But I could do even more exotic things:

# no base-class, but has_many triggers mixin
class Person
  has_many :opinions
end

Or

Person = Model :has_many=>:opinions, :validates_presence_of=>:first_name

Or

# creates a Person class!!
person {has_many :opinions; validates_presence_of :first_name}

Or how about:

# creates MyDB::Person, MyDB::Opinion, & other classes automatically
module MyDB
  tables :all
  naming_conventions :capitalized, :singular
end

One of these choices is clearly better than all the others. (Which one?)

The unconventional wisdom here is that your syntax should be chosen for the domain, not by the language. In order for this to work, you must be able to think creatively about the domain you are working in.

The classic counter-argument is "our developers aren't smart/skilled/experienced enough to take advantage of this." Riiight. If your developers aren't skilled enough to think creatively about the domain you are working in, you have way bigger problems.

(Updated to fix typo in example five, thanks Scott!)