【case文】

case 比較したいオブジェクト
when 値１ then
　文１
when 値２ then
　文２
when 値３ then
　文３
else
　文４
end

※thenは省略可能


（例）case.rb
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#!/usr/local/bin/ruby

tags = ["A", "IMG", "PRE"]

tags.each{|tagname|
　case tagname
　when "P","A","I","B","BLOCKQUOTE"
　　print tagname, " has child.\n"
　when "IMG","BR"
　　print tagname, " has no child.\n"
　else
　　print tagname, " cannot be used.\n"
　end
}
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