G'day Andre_C10002,

Welcome to the monastery.

I'm not in a postion to test this, but one problem may be all the embedded spaces and newlines in your DSN. Try writing it more like this:

my $dbh = DBI->connect(join('',
        'DBI:mysql:database=_DATABASE_;host=_HOST_;',
        qw{
            mysql_ssl=1;
            mysql_ssl_client_key=/etc/mysql/certs/client-key.pem;
            mysql_ssl_client_cert=/etc/mysql/certs/client-cert.pem;
            mysql_ssl_ca_file=/etc/mysql/certs/ca-cert.pem
        }
    ),
    '_SSL_USER_',
    '_SSL_USER_PWD_'
) || die DBI->errstr;
[download]

Another potential issue is what you really have for the placeholders you show (e.g. '_SSL_USER_PWD_'). If any of those are (or evaluate to) strings with special characters (e.g. "pass$word"), you may need to escape the special characters. There's several ways of doing this depending how you're actually getting that data into connect(). Some examples: "pass\$word", 'pass$word', q{pass$word}, "\Q$variable_holding_password\E".