When I try to open this perl script from my browser I get this:

You have chosen to open: installer.pl which is a Perl Script:
What should Firefox do with this file?

I already installed libapache2-mod-perl2, clear the cache, restarted Apache and still get the same error. I'm trying to install the otrs Trouble ticket software. I did an apt-get install otrs and the files are in this path:

/usr/share/otrs/bin/cgi-bin

Should I move them to /var/www so Apache can see them? Not sure if that is the case. I had similar error with PHP but I was able to fix that by intalling the PHP parser for Apache.

Thanks for any help.

Apache will only run a CGI script if it's in a scriptalias directory that it knows about. You can either move the file to a valid Apache script directory or modify the Apache config to serve up files in the directory the application put itself into. Note that (1) Apache generally expects CGI scripts to have a .cgi extension and (2) to execute a CGI you must go through a Web server -- opening the script as a file:// in the browser won't work.

Ok, Bt so should I move the files to /var/www where Apache knows where to look for them? Thanks!

well only if /var/www has been marked as a cgi directory.

You can do it by extension as well (I think php likes to do this so you can mix in the html files with php files in the same directory, not advisable though).

You need to speak to the person who installed Apache on the system - as it seems to find your installer.pl file if that is in /usr/share/otrs/bin/cgi-bin/ and that is the only file named installer.pl (find / -name 'installer.pl').

installer.pl should be marked as executable for the server, cgi works by allowing the server to call the file directly and the shell used to call has the environment variables set for things like form post's and query's, no magic is happening here in the server it is just like a user calling the file. The output is then redirected so the server can then put it on the appropriate http response port.

Now if it is executable and the only file called installer.pl on your system you can start to suspect that the apache directive for /usr/share/otrs/bin/cgi-bin has been setup incorrectly.