equality.rb

#!/bin/env ruby

foo = "someval"

puts "==="
puts foo.class === "String"
puts foo.class === String

puts "\n=="
puts foo.class == "String"
puts foo.class == String

puts "\neql?"
puts foo.class.eql? "String"
puts foo.class.eql? String

puts "\nCase"
case foo
when String
    puts "STRING"
when "String"
    puts "QUOTED STRING"
end

puts "\n Case class: #{foo.class}"
case foo.class
when String
    puts "STRING"
when "String"
    puts "QUOTED STRING"
end

output

ruby foo.rb
===
true
false

==
false
true

eql?
false
true

Case
STRING

 Case class: String

why ?