if($tmp eq 'F'){
        ;    # do nothing, spot held for clarity
    }elsif($tmp =~ /[MICL]/){
        ...  # do something ...
    }else{
        ...  # do something 
    }
}

##</code><code>##

$tmp = $some_result;
my $handler = $handlers{$tmp};
&$handler(...) if $handler; # might be undef, as in 'F' case