You're totally right, cf Re^20: Using STDIN after exec() with ActiveState Perl

edit: oh actually I guess you meant an API call in the dynamic library I load, which would allow me to avoid relying on environment variables. Yes you're right, unfortunately there is no such API function to set the write directory (only data directories). And if it was added now, I wouldn't be able to use it anyway since I have to maintain backward compatibility with older versions of this library.