**ePN /usr/lib/nagios/plugins/check_mem.pl: “Argument “-c” isn’t numeric in numeric eq (==) at (eval 5) line 322,”.

I used the plugin and when checked manually it works, but in the CGI i dont get the expected result. In the status information it should show soothing like ‘OK – 33.5% (2557620 kB) free.’, but what i get is ‘**ePN /usr/lib/nagios/plugins/check_mem.pl: “Argument “-c” isn’t numeric in numeric eq (==) at (eval 5) line 322,”.’

Why is it so?