[exim] send mail to a script

Hello,

I'm tasked with configuring exim to send emails with a specific recipient format to a script to process the emails.

I'm confused with when and how to use routers and transports, directors or system filtering/forwarding (or some combination thereof).
I see in past emails that I might want to use a pipe in the alias file to do this (and configure transport and routers in the .conf file), but someone told me to use system filtering.

I've tried reading a lot of documentation, but it's still not clear to me exactly what is the best way to go about this.
Could someone help start me out or point me to something that might be helpful? Please let me know if I should give more information.

Thank you...!