If you want to do exclusive searching, you can approach it a couple ways. here is something I thought of just now. If i have more solutions, i'll post.
How exactly are you searching? Do you have the entire file in a database? and you are using a simple mysql query to search?
If so, then you have to do the following:
use ereg replace on the field you are searching for and replace the instances you find with nulls or empty strings "". Then make this in a field itself in mysql using AS in your select query and then in your WHERE clause, you can say something like WHERE newfield LIKE '%$word%'.
NOTE: in the above, you do NOT create a new field in the table. By creating a new field, I meant doing it in the select...
I'll try to come up with the SQL query for this in a little while and post it here or email you.
In the meanwhile, if you can post your current SQL query, that can speed things up for both you and me (for me because i can see what field names you are using and whether you are already doing something weird with them).
-sridhar