Personally I try to avoid editing HTML files directly (in a CGI context that is). You might want to check SSI (Server Side Includes), which basically can insert script output in a HTML file (without actually changing the HTML file). The other way is have a pure CGI guestbook (no/minimal HTML files).
Greetz
Beatnik
... Quidquid perl dictum sit, altum viditur.
Sorry for my vagueness before, I'll try to clear some things up..
The file that the guestbook writes to is more or less a flat-file database WITHOUT delimiters, so there isn't a way to single out entries unless a name, address, or zipcode-query is done to point to a certain area of the file to be edited.
Ultimately, I would like the script to be able to edit the flat-file html page thru an admin. page like the one submitted by "Tachyon" (see above)....just the ability to edit the contents of a flat-file database(without obvious delimiters) over the web.
Here is the guestbook script that creates the flat-file:
http://204.33.180.159:8080/guest.txt