Just checking in on a couple of issues here.
1/ Is Q1 a single response question or a multiple response question?
2/ Perl is case sensitive so we need to ensure your list name is entered exactly as you have defined it.
If Q1 is a single response question, try this ...
Begin Unverified Perl
If Q1 is a multiple response question, change the following ...
I have assumed your parent list is defined as "parentlist".