Check UNIX Memory Usage

I just copied the check_unix_mem_usage.pl into my nagios libexec folder.

/usr/local/nagios/libexec/

And when I try to run the plugin locally and check the output it gives me only the following line.
I ran the command as follows:
/usr/local/nagios/libexec/check_unix_mem_usage.pl

And the output was :
Setuid/gid script is writable by world.

Please help me to get this done.
Thanks.