Good and interesting post Purdy! I've been playing with the code and following the evolution of the replies. I've not used LOLs before and found the array syntax(es) not very intuitive. I borrowed DragonChilds array initialization technique and used a map/grep strategy similar to AidanLees. For some reason it is easier for me to grasp  @{$listA[0]} representation than to break it down further to  $_->[0] constructs. Maybe more practice (and learning some OOP) on my part will help.

use strict;

my (@listA, @listB);
$listA[0] = [qw(1 foo bar)];
$listB[0] = [qw(1 bar baz)];

my %hash = map { $_ => 1 } @{$listA[0]};
my @c = grep {! exists $hash{$_}} @{$listB[0]};

print "$_\n" foreach (@c);
[download]

--Jim

Update: changed  @listX[0] as per seanbos reply. Thanks seanbo, I originally had it right but forgot to change it back after an unfruitful experiment. Should've used -w.