In a scenario where a contact center is implementing a new customer interaction script using the Script Editor in Cisco Unified Contact Center Enterprise, the team needs to ensure that the script can handle various customer intents effectively. The script must include decision nodes that evaluate customer responses and direct the flow accordingly. If a customer indicates they want to check their account balance, the script should branch to a specific subroutine that retrieves this information. What is the primary function of decision nodes in this context, and how do they enhance the script\'s functionality?