class Sass::Constant::Operation

def perform
  literal1 = @operand1.perform
  literal2 = @operand2.perform
  begin
    literal1.send(@operator, literal2)
  rescue NoMethodError => e
    raise e unless e.name.to_s == @operator.to_s
    raise Sass::SyntaxError.new("Undefined operation: \"#{literal1} #{@operator} #{literal2}\".")
  end
end