my $dsn = 'DBI:mysql:database=testdb;mysql_read_default_file=creds.txt';
my @dsns = (
 $dsn,
 '', # username is read from file
 '', # password is read from file
 {"RaiseError" => 1, "PrintError" => 1}
);
my $dbh = eval { DBI->connect(@dsns) };
die $@ if $@;

##</code><code>##

[client]
user=testuser
password=apass

##</code><code>##

my $dsn = 'DBI:MariaDB:database=testdb;mariadb_read_default_file=creds.txt';
...