gistfile1.txt

class MyException < StandardError
  attr_reader :arbitrary_value
  def initialize(message, arbitrary_value)
    super(message)
    @arbitrary_value = arbitrary_value
  end
end

e = (raise MyException.new('this is the regular message', 'my value') rescue $!)
# this is a shortcut for:

begin
  raise MyException.new('this is the regular message', 'my value')
rescue MyException => e
  e.inspect #=> #<#<Class:0x007ff06943f808>::MyException: this is the regular message>
  e.arbitrary_value #=> "my value"
end