US Citizen Visiting Ireland / Re-Entry

Hello all! I am new to the LonelyPlanet forum! I will be taking a trip next month through Europe starting with Ireland. It is my understanding that as a US citizen I am not required to have a visa to visit Ireland for up to a 90 day stay. I am starting in Ireland and will be travelling to other countries in Europe (England, Belgium, France, Switzerland). My question is, are there any complications with entering Ireland again after I have left and gone to other countries? This will all be within a month time period. I purchased round ticket flights to and from Dublin because it saved me some money.

So, am I able to leave and re-enter Ireland as long as it is within the 90 days?

Thanks!
Chris