Hello monks. I learned how to use Tie::DBI a long time ago, and found a snippet of code that fit perfectly into a script I was writing. This code throws a "Can't use an undefined value as a HASH reference..." when I use it in my new script, but works perfectly fine as it is. Seems odd to me, can't figure out why it works, but not when placed in my script.

So the snippet of code I used is this:

use Tie::DBI;
use List::Compare;

tie %h,'Tie::DBI',{db       => 'mysql:db',
                   table    => 'table',
                   key      => 'k',
                   user     => 'root',
                   password => 'rootpass',
                   CLOBBER  => 1};
%day = ('the' => '1', 'tuesday' => '2', 'wednesday' => '3');

$lc = List::Compare->new([keys %day],[keys %h]);
@intersections = $lc->get_intersection;

foreach $intersection (@intersections) {
    print $intersection, "\n";
    print $h{$intersection}{value}, "\n";    
}

exit;
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In my script, the code looks like this:

my %count;
#tie hash to the MySQL DB
tie my %h,'Tie::DBI',{db       => 'mysql:db',
                   table    => 'table',
                   key      => 'k',
                   user     => 'root',
                   password => 'rootpass',
                   CLOBBER  => 1};

#split @titles by word, then to-lower, then remv special chars
my @intersections;
my $lc;
foreach my $title (@titles) {
    my @words = split(" ", $title);
    foreach my $word (@words) {
        $word =~ tr/A-Z/a-z/;
        $word =~ s/[^a-zA-Z0-9]*//g;
        $count{$word}++;
        print $word, "\n";
    }
}
$lc = List::Compare->new([keys %count],[keys %h]);
@intersections = $lc->get_intersection;

foreach my $intersection (@intersections) {
    print $intersection, "\n";
    print $h{$intersection}{value}, "\n";
}
[download]

The error happens on the line:

print $h{$intersection}{value}, "\n";
[download]

The MySQL db is structured like this:

id|k        |value
--+---------+--------------
# |theword  |1 (word count)
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Also, in my script '@titles' contains sentences that will be split by word into a hash.

The first snippet of code returns

the
20
[download]

Thanks in advance, I'm honestly expecting a really stupid bit of something I overlooked, but any advice would be welcome. Thank you. **EDIT** Updated based on philipbailey's comment. Moved the list comparison out of the for loop. Still getting undefined.

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