I will be sharing the same script across multiple domains, and would rather not have to maintain copies. Having the script in a common place is less fragile to version inconsistency.
Also, I was keen to share code between the cgi script and my .procmail response script, since they both collude to provide a related service. It just feels wrong to me to point my .procmail code at ~/mydomain.com/cgi-bin/foo.pl, since that entry point is agnostic of which domain I am using.
I suppose I can use some clever wonking in the .htaccess file for the root to re-map the cgi-bin sub-directory of the document root to a different directory in my home dir?