How to edit check_mem for using it through NRPE?

The author states: “This plugin may be used as nrpe plugin and checks the amount of memory free, used and total available by using the linux “free -mt” command.”, but since i don’t understand perl i cannot figure out how to do this.
I`m using check_mem 1.5 by rouven downloaded from nagiosexchange.org.
Thanks in advance.

Stupid permission problem. Works fine now.