At first the command definition has to be done in the Nagios configuration by the following (i.e.):

define command {
  command_name  check_cisco_wlc
  command_line  $PATH$/check_cisco_wlc.pl -H $HOSTADDRESS$ -C $SNMP_COMMUNITY$ -x $ARG1$
    -w $ARG2$ -c $ARG3$
}

Afterwards a service can be configured in the Nagios configuration by setting the 'check_command' for example to the following:

check_command  check_cisco_wlc!clients!200!250

This command would check the amount of clients associated with the WLC. A WARNING will be evaluated if this amount is between 200 and 250. If the value is even above 250, status will be set to CRITICAL.

perl check_cisco_wlc.pl -h

check_cisco_wlc.pl - SNMP Cisco WLC monitor PlugIn for Nagios in version 0.3
Copyright (C) 2013 Stefan Heumader 

check_cisco_wlc.pl usage: check_cisco_wlc.pl [-v] -H  -C  [-p ] -w  -c  [-t ] [-V] -x 

-h, --help
        print this help message
-V, --version
        prints version number of Nagios PlugIn
-v, --verbose
        print extra debug informations
-H, --hostname=HOST
        name or IP address of host to check
-C, --community=COMMUNITY NAME
        community name for the host's SNMP agent
-P, --port=PORT
        SNMP port (default 161)
-w, --warn=INTEGER
        warning threshold
-c, --crit=INTEGER
        critical threshold
-x, --category=STRING
        defines which information should be read, the following categories are available:
                temperature  - temperature
                cpu          - cpu utilization
                memory       - used memory in percent
                clients      - amount of associated clients
                accesspoints - amount of associated accesspoints

The actual version supports the following categories to evaluate:

• temperature temperature
• cpu cpu utilization
• memory used memory in percent
• clients amount of associated clients
• accesspoints amount of associated accesspoints