use strict;
use warnings;
use Data::Dumper;

my %data;
while (<DATA>) {
    chomp;
    my ($lot, undef, $make, undef, $city, $state) = split /,/;
    $data{$lot}{$make}++;
    $data{$lot}{location} = "$city,$state";
}
print Dumper(\%data);

__DATA__
lot1,new,honda,civic,cincinnati,oh
lot1,used,chevy,impala,cincinnati,oh
lot1,new,honda,civic,cincinnati,oh
lot1,used,chevy,impala,cincinnati,oh
lot1,new,cadillac,escalade,cincinnati,oh
lot2,new,buick,sentry,houston,tx
lot2,used,ford,ranger,houston,tx
lot2,new,buick,sentry,houston,tx
lot2,used,ford,ranger,houston,tx
lot2,used,ford,ranger,houston,tx
lot3,new,ford,ranger,lexington,ky
lot3,used,cadillac,escalade,lexington,ky
lot3,used,cadillac,escalade,lexington,ky
lot4,new,ford,f150,chicago,illinois
lot4,new,ford,f150,chicago,illinois
lot4,new,ford,f150,chicago,illinois
[download]

which prints out;

$VAR1 = {
          'lot3' => {
                      'location' => 'lexington,ky',
                      'ford' => 1,
                      'cadillac' => 2
                    },
          'lot1' => {
                      'location' => 'cincinnati,oh',
                      'cadillac' => 1,
                      'chevy' => 2,
                      'honda' => 2
                    },
          'lot2' => {
                      'location' => 'houston,tx',
                      'ford' => 3,
                      'buick' => 2
                    },
          'lot4' => {
                      'location' => 'chicago,illinois',
                      'ford' => 3
                    }
        };
[download]

awesome. that works great. one more quick question... what would be the best way to remove any trailing/leading whitespace from the elements, as some of them have it? i know how to remove leading/trailing whitespace... but is there a way to do it on the current hash?

You should remove whitespace before loading data into the hash, not after it is in the hash, especially if the hash keys have whitespace.