Paul Graham has developed his own language, called Arc, a dialect of Lisp. He writes about Arc:

I didn't decide what problems to work on based on how hard they were. Instead I used what might seem a rather mundane test: I worked on things that would make programs shorter.

To demonstrate the powerful brevity of Arc, he has offered a challenge.

I'm going to propose a simple problem as a challenge. We'll collect solutions in each of the popular languages, and compare their lengths. Here it is:

Write a program that causes the url said (e.g. http://localhost:port/said) to produce a page with an input field and a submit button. When the submit button is pressed, that should produce a second page with a single link saying "click here." When that is clicked it should lead to a third page that says "you said: ..." where ... is whatever the user typed in the original input field. The third page must only show what the user actually typed. I.e. the value entered in the input field must not be passed in the url, or it would be possible to change the behavior of the final page by editing the url.

Though simple, as such tests have to be, this is not a contrived example. Web apps have to do this sort of thing all the time. Nor does it depend on some sort of esoteric libraries that Arc has and other languages don't; this is all stuff that any language used to write Web apps would have to have already.

Here's the answer in Arc:

(defop said req
  (aform [w/link (pr "you said: " (arg _ "foo"))
           (pr "click here")]
    (input "foo") 
    (submit)))
[download]

I think The example from Arc is short enough that there really can't be any meaningful competition. Suppose there is a shorter solution somewhere. It can't be much shorter, so that's not much of a win. If it is a lot shorter, it's probably incomprehensible.