@Fastnlight Given that this entry itself doesn't
require that there be something after the
(?:@aol\.com)?
, having that portion be possessive will result in the regex not matching at all in cases where the "@aol\.com" is not followed by a non-word character (e.g., "@aol.coma"), which the bookending would require. Having it be possessive results in the "@aol.com" not being able to be given back, even if that's necessary for the overall matching of the regex.
Here is a regex101.com example of this. While the cases which will fail should be rare, I don't think this is what you intended.