What if your search assigned an ID number to each visitor, and you used that ID number with a CGI image generation script to either pull their search terms, or simply retrieve a pre-built image associated with that ID?

# in the parent CGI script
my $id = get_user_id;          # just give them a new ID
build_image($id, @arguments);  # or store the arguments
                               # in a database or something

print "<img src='/cgi-bin/fetch_image?$id'>\n";

# or you can be cool and use CGI PATH_INFO stuff:

print "<img src='/cgi-bin/fetch_image.cgi/$id.gif'>";
[download]

Then either build the image from the stored information, or retrieve a temp file that matches the ID and send the resulting image, removing the file when it's done.