Just do this:
if ($read(seen.txt,s,$nick $+ :)) { write -ds $+ $readn seen.txt }
else write seen.txt Whatever you're writing when there isn't something to delete.
Perfect, except, that finds a way that a word is the file once. I kind of wanted it to count the number of times a starting-line word word is in there 5 times, then keep overriding the last 5th.
Thanks.
-Neal.