my $op = $query->param('option') || 'Login';

if ($op !~ /^[a-z0-9_]*$/i) {
      $op="NotAllowed";
}
eval "require $op";
die "Couldn't find Class $op : ".$@."\n" if $@;
$op->perform(...);

##</code><code>##

my $mods = {showOverview=>"showOverview", Login => "Login"}
my $op = $mods->{$query->param('option')};

eval "require $op";
...