$dsn = 'DBI:mysql:ciprestest:localhost';
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As jaco already pointed out you need to spruce up that DSN a bit.

my $database="ciprestest";
my $host="localhost";
my $DSN=sprintf("DBI:mysql:database=%s:host=%s",
                $database,$host;
my $dby = DBI->connect($DSN,$dbuser,$dbpass,
                 {RaiseErrors => 1 ) 
    or die $DBI->errstr;
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Also you might want to make sure your permissions within MySQL are correct. If the user@host combination is not set up with permissions to access the database you'll get bounced out. Check tables mysql.Db, mysql.User and mysql.Host and make sure they are set up correctly.