Perseverations are common to ASD. They are like OCD-lite. (Unlike OCD, they subside when there is closure.)
Wow, so I googled perseverations this morning - WOW. This is EXACTLY what I've struggled with my whole life. I got the OCD diagnosis because of this, but since I really don't have compulsions, I knew it didn't fit. This is it!!! Thanks so much, I'm so glad I came here and read this thread! Yet another thing that makes perfect sense that didn't before. (As an aside, this is what frustrates me *so much* about not having been diagnosed properly - I'm 31 years old and just learning this now. If I had been able to have this information years ago, it would have changed my life - but that information was withheld from me due to the lack of a diagnosis.)