Remarks

Just run it with no argument:

ruby entry.rb

I confirmed the following implementations/platforms:

• ruby - version 1.0-971225 (i386-netbsd)
• ruby - version 1.1a9 (i386-netbsdelf)
• ruby 1.2(98/12/25) [i386-netbsdelf]
• ruby 1.4.6 (2000-08-16) [i386-netbsdelf]
• ruby 1.6.8 (2003-03-26) [i386-netbsdelf]
• ruby 1.8.7 (2008-05-28 patchlevel 5000) [i386-netbsdelf]
• ruby 1.9.3p392 (2013-02-22 revision 39386) [i386-netbsdelf]
• ruby 2.0.0p0 (2013-02-24 revision 39474) [i386-netbsdelf]
• ruby 2.1.0dev (2013-04-11 trunk 40225) [i386-netbsdelf]

Description

An executable, succinct, and completely self descriptive haiku written in ruby.

• This program is just executable, and has no feature at all. So this is "the most Transcendental, Imbroglio Ruby program."
• This program exploits a kind of Ruby's design issue that a method does not check if it accepts block argument or not. Also, it reveals a spec-level bug that there is is_a? method but that there is not is_an?. So this illustrates "some of the subtleties (and design issues) of Ruby."
• This program works on almost all Ruby implementations. So this shows "the robustness and portability of Ruby interpreters."

Internals

This exploits the fact that Ruby (foolishly) keeps the specs:

• A method does not check if it accepts block argument or not.
• An identifier that may be a method is not evaluated until it is needed.

Limitation

• Unfortunately, it does not run on ruby version 0.49 because of extremely-different syntax.
• Also, it does not run on ruby version 0.95 because nil does not have is_a?.