Ruby percentage notations

The percentage notation in Ruby is clearly inspired by Perl. It allows generating plain and interpolated Strings, String Arrays, Symbol Arrays, Shell commands and regular expressions.
Basically the notation consists of a unique identifier (character), a prefixed ‘%’ and the delimiters.
The delimiters can be any alpha-numeric character.
Some examples by means of the String percentage notation:

%(Ruby is awesome) # => "Ruby is awesome"
%[Ruby is awesome] # => "Ruby is awesome"
%%Ruby is awesome% # => "Ruby is awesome"
%.Ruby is awesome. # => "Ruby is awesome"

Brackets do not need to be escaped, if they are part of the content and include both the opening and the closing bracket (even nested brackets). That only works, when using bracket delimiters:

%(Ruby (is) awesome) # => "Ruby (is) awesome"
%[Ruby [is awesome]] # => "Ruby [is awesome]"
%<Ruby <<is> awesome>> # => "Ruby <<is> awesome>"

All remaining alpha-numeric characters have to be escaped:

%-Ruby \-is\- awesome- # => "Ruby -is- awesome"

That is why only brackets should be used as delimiters. Furthermore brackets increase readability, especially when used in following a style guide rule (take look at the brief overview table).
A couple of simple and some interpolated percentage notations:

language = 'Ruby'

%q('Simple' "non-interpolated" String.) # => "'Simple' \"non-interpolated\" String."
%Q(Interpolated "#{language}" String.) # => "Interpolated \"Ruby\" String."
%(Interpolated "#{language}" String (default).) # => "Interpolated \"Ruby\" String (default)."
# Simple non-interpolated String Array:
%w[Ruby Javascript Coffeescript] # => ["Ruby", "Javascript", "Coffeescript"]
# Interpolated String Array:
%W[#{language} Javascript Coffeescript] # => ["Ruby", "Javascript", "Coffeescript"]
#  Simple non-interpolated Symbol Array:
%i[ruby javascript coffeescript] # => [:ruby, :javascript, :coffeescript]
# Interpolated Symbol Array:
%I[#{language.downcase} javascript coffeescript] # => [:ruby, :javascript, :coffeescript]
%x(echo #{language} interpolated shell scripting command)
# => "Ruby interpolated shell scripting command\n"
%r{/#{language} regexp/i} # => /\/Ruby regexp\/i/

The percentage notations as a brief overview:

Literal Description Bracket type
%q Simple non-interpolated String ()
%Q Interpolated String ()
% Interpolated String (default) ()
%w Simple non-interpolated String Array []
%W Interpolated String Array []
%i Simple non-inteprolated Symbol Array []
%I Interpolated Symbol Array []
%x Interpolated shell command ()
%r Interpolated regular expression {}