It is almost certainly some limit on the number of connections that you have to the database - I think you will find that if you move the :

       
 my $dsn = 'DBI:mysql:*database*:localhost';
 my $db_user_name = '*username*';
 my $db_password = '*password*';
 my $dbh = DBI->connect($dsn, $db_user_name, $db_password);
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outside the foreach loop then all your troubles will go away.

/J\