# this isn't really the assignment, but showing an example
$listA[0] = ['1','foo','bar'];
$listB[0] = ['1','bar','baz'];

# these prints fine
print 'First record from @listA: ' . (@{$listA[0]})[0] . "\n";
print 'First record from @listB: ' . (@{$listB[0]})[0] . "\n";

# We first want to get a list of records
# in B that aren't in A
my ( $a, $b );
@listToExpire = grep ( ($b = (@{$_})[0] &&
 grep( ($a = (@{$_})[0] && $b != $a), @listA )), @listB );