To use them, you will need to put the two perl files in the /usr/lib/zabbix/externalscripts directory and make them executable by the zabbix user.
The first script mysql_status_check.pl is used by the individual service checks to populate the data. The scond script snmp_mysql_status_discovery.pl is used in the discovery to pull all IP's from the host via snmp so if you have multiple mysql instances on the same server, all will be monitored.