You can change the list in which you customers get added to, but our system would not break them into 2 lists when importing.
You can change the default list on your form by:
You also could add two different lists to the form, however the customer would have to choose which list they would like to be added to.
Please get a feature for A/B testing on constant contact. It is a hastle to take the lists, then seperate them into seperate lists, then send seperate emails.
Constant Contact should have an A/B testing tool so that splitting lists is not such a manual process. It would help us all be better email marketers!
UPDATED: June 2018
If you are working in a 3GE template, Subject Line A/B Testing can be turned on in the scheduling of your email campaign.
Hello @EricM298 ,
We now have a feedback area of the Community where you can pass this suggestion along. Feel free to post this topic here. As you have seen we do not have this feature available currently; however by posting in the feedback area others can vote on the idea. If the idea gets more votes it has a greater chance of being implemented in the future.