Mea culpa. I completely mis-read your problem.

If you want to run code inside the file "cgi-bin/weather/weather.cgi", why are you opening it and reading its contents?

The next question is what does the code inside that file look like? If it's a stand-alone program that uses (for example) LWP to obtain the weather info from another website, then to get that data into your calling script will depend on what that script does with the data? Write it to a file, print it to STDOUT etc.

I think you will need to post the contents of that file before anyone will be able to advise you on how to get the data it generates into your program.