Your eval won't catch anything unless you set the RaiseError attribute on your database handle:

$dbh  = DBI->connect($DSN,$user,$pw, { RaiseError => 1 })
|| die "Cannot connect: $DBI::errstr\n" unless $dbh;
[download]

Otherwise, check the results of all of your $dbh calls for undef and do something with $DBI::errstr yourself.