This may or may not help your prob - how about an even simpler unit test:

use strict;
use Text::CSV;
use Data::Dumper;

my (%report,@headers);
my $csv = Text::CSV->new();

while(<DATA>) {
   die unless $csv->parse($_);
   if ($. == 1) {
      @headers = $csv->fields();
      $report{headers} = \@headers;
   }
   else {
      my @row = $csv->fields();
      push @{$report{data}}, {map{$headers[$_]=>$row[$_]} (0..$#row)};
   }
}

print Dumper \%report;

__DATA__
foo,bar
333,aaa
444,bbb
555,ccc
[download]

Update:
"This fails because, as I mentioned, I don't have direct access to the CSV data and thus cannot use Text::CSV"

I probably chose the words 'unit test' poorly. When i find myself in this situation i try to back away and try another route. I only used Text::CSV to abstract that portion of the problem, as the data structure was what was giving you the trouble.