A switch/case would be a great enhancement to speed and efficiency of not only runtime but of coding too. Consider the following script:

if (%command == ban) { ...
} elseif (%command == unban) { ...
} elseif (%command == op) { ...
} elseif (%command == deop) { ...
} elseif (%command == voice) { ...
} elseif (%command == devoice) { ...
}

%command must be evaluated 6 times here in an unbalanced situation (the first commands will execute much sooner than commands at the end of the clause).

In a switch/case:

switch (%command) {
case (unban) ...
case (ban) ...
case (op) ...
case (deop) ...
case (voice) ...
case (devoice) ...
}

Here, %command is evaluated once, the code is 10 times clearer, and if all cases are literal strings, mirc could internally use a hashtable which would mean that all commands would take the same amount of time to execute regardless of where they are on the sequence.