Synopsis:

on [<modes>]set [<serial#>] [-|^]<match> { <action> }

Description:

This hook is triggered whenever a /set is issued.

$0	name of variable to be set. will be “set-error” if an invalid SET variable was specified
$1-	value the variable will be set to. will be “No such variable “FOO””, where FOO is the invalid SET variable if $0 is “set-error”

To make sure set security stays on:

 on ^set "security %" {
    xecho -b You cannot set SECURITY off!
    set exec_protection 7
 }

To warn of all invalid /SET attempts:

 on ^set "set-error *" {
    xecho -b $1-. Please try again
 }