(Note that I put '{' & '}' around local ... warn Dumper ... to limit the scope of changes to variables in Data::Dumper package. (So much for avoiding OO interface. ** sigh ** ))

Instead of dumping just the idEnrollee field, you could try dumping $RS_UsersToRemind: if everything else is there besides idEnrollee then surely you might have problem|mismatch in your SQL or the table. Somebody familiar with your database and/or associated driver would be able to provide you with a better clue.