Getting current active user

http://www.movabletype.org/documentation/man/MT/App.html#%24app-%3Euser

sub _my_mode_handler {
    my $app = shift;
    my $user = $app->user;
}

I guess I should have been more clear. I'm not actually writing a plugin per-say, but using MT's system to get the information that I need. My script resides in the mt directory, but has no ties to the system itself.

So for example, I'm getting the recent entries by:
use MT::Bootstrap;
require MT::Entry;

my $entry = MT::Entry->load($entry_id)

where I'm getting the ids from database queries. Is there any similar way to go about getting the current active user? Maybe with cookie/request variables?

What are you trying to do?