I've done:

up2date -i htdig

'till here, everything ok, but now I want to use it on my virtual servers... www.htdig.org does not explain it very well, and the way rpm installs it seems like works only for one domain, now i want to run it as a CGI on Apache, copied the /usr/share/htdig files into a dir on my server, also done a hard link on /home/httpd/vhosts/mydomain.com/cgi-bin to htsearch
but I keep on getting this error on the browser:

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Also looked no my error_log and I keep on getting this error message:
Premature end of script headers: htsearch, referer: http://www.mydomain.net/search/index.html


Any clues on what else can I do to make it work ...¿?

Check the apache logs, there could be multiple problems. You can try to execute the script from command line, most likely a perl module is missing.

From command line works perfect, perl not missing...
I believe most likely I have something wrong with config file, may be it cant find it (I've put it at /cgi-bin/ dir too). From the form where I type search words i tell it that config file is htdig...
I've allready checked apache logs as I say it on my post, and that is the error I'm getting (on my last post too).


Anyway... is there any tutorial on how to integrate htdig on virtual domains the way they are set up on plesk ??

Any other Free search engine...?

I suggest you to check whether there is no problem with the paths (they should be all absolute).