Can you access "only" the URL of the second CGI script or oven the script itself (on the filesystem)?

In the first case, you should call that script using LWP::UserAgent within the body of the first script, and then parse the output of HTTP response.

In the latter case, you can call the second script using system functionlike this:
system "script2.cgi arg1=val1 arg2=val2 var3=val3"

Depending on what you're trying to achieve, you might also consider using more powerful tools like SOAP::Lite.