Rubyのcase式で気を付けること ref: http://qiita.com/items/2796

arara_case.rb

require './strange_case.rb'

strange_case( "1" )       # => true
strange_case( :"1" )      # => true
strange_case( 1 )         # => true
strange_case( [1, 2, 3] ) # => false
strange_case( {"1"=>1} )  # => true
strange_case( (1..3) )    # => false
strange_case( /.*/ )      # => false
strange_case( Fixnum )    # => false

array_case.rb

def array_case(year)
  case year
  when [*1925, 1926]
    "T"
  when [*1926..1989]
    "S"
  else
    "H"
  end
end

array_case(1926)          # => "H"
array_case(1973)          # => "H"
array_case(2012)          # => "H"

ex_array_case.rb

class Array
  alias :=== :include?
end

def ex_array_case(year)
  case year
  when [*1925, 1926]
    "T"
  when [*1926..1989]
    "S"
  else
    "H"
  end
end

ex_array_case(1926)       # => "T"
ex_array_case(1973)       # => "S"
ex_array_case(2012)       # => "H"

range_case.rb

def range_case(year)
  case year
  when 1912..1926
    "T"
  when 1926..1989
    "S"
  else
    "H"
  end
end

range_case(1926)  # => "T"
range_case(1973)  # => "S"
range_case(2012)  # => "H"

strange_case.rb

def strange_case(obj)
  case obj
  when obj
    true
  else
    false
  end
end

strange_case( "1" )       # => true
strange_case( :"1" )      # => true
strange_case( 1 )         # => true
strange_case( [1, 2, 3] ) # => true
strange_case( {"1"=>1} )  # => true
strange_case( (1..3) )    # => false
strange_case( /.*/ )      # => false
strange_case( Fixnum )    # => false