In the second line, $myFile is not defined. I think you wanted to use $file.
You are printing "No fork: $!\n" without first printing "Content-type: text/html\n\n"; This causes 500 Fatal Error.
You are forking a process that execs to unzip a file. The main process however sits idle waitpiding for the child to exit. You should've just used system to unzip the file and return to the user.
You can also use the Archive::Zip module instead of firing another process just to do the unzipping.