Pfsense disc space monitoring thru SNMP request

Hi
I am in the process of monitoring pfsense disc usage thru SNMP
At the moment I am testing to get the /root partition usage and size with following commands

root@xxxx:/usr/lib/nagios/plugins# ./check_snmp -H xxx.xxx.xxx.xxx -o 1.3.6.1.2.1.25.2.3.1.5.4 -C xxxx
SNMP OK - 3043688 | iso.3.6.1.2.1.25.2.3.1.5.4=3043688

root@xxxx:/usr/lib/nagios/plugins# ./check_snmp -H xxx.xxx.xxx.xxx -o 1.3.6.1.2.1.25.2.3.1.6.4 -C xxxx
SNMP OK - 835011 | iso.3.6.1.2.1.25.2.3.1.6.4=835011

to set alarms i need to set the relation between them thru a seperate script and then set the thresholds

Do you have any example for such script (command) that calls the check snmp and calculate the thresholds? in Perl?

best regards

Davoud Azimian