Hi anonymous, the owner of new files created by an cgi process is the user that is running apache. usually this is www-data, apache or just nobody.
I don't think File::Temp offers setting of file permissions but you can do this by either.
- chmod 0755 ,$file;
- changing apache config to set the file create mask to 755 or whatever you like

In windows I don't know what would happen since I never work on windows systems anymore ;)

Cheers,
Rob