Most optimization opportunities are in the inner loop. Exit the loop as quickly as possible for most cases.

split() and the array cleverness is a little bit slow, so this skips it most of the time:

    while (<IN>) {
        $numlines++;  # Remove for more speed
        next if not /^McDarren\t/;
        chomp();
        my ($user,$level) = (split /\t/)[0,3];
        next FILE if $level <= $currlevel;
        print "$file $user $level";
        print "Processed $numlines lines in ".
              "$numfiles files (total files:$totalfiles)";
        exit;
    }
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