class Regexp::Parser

def sequence_operation(klass, token)
  if node.last.is_a?(klass)
    self.node = node.last
  elsif !node.is_a?(klass)
    operator = klass.new(token, active_opts)
    sequence = operator.add_sequence
    sequence.expressions = node.expressions
    node.expressions = []
    nest(operator)
  end
  node.add_sequence
end