How to extend bash shell ?

Question

Hello, would like to add new functionality to the bash shell. I need to have a queue for executions.

What is the easy way to add new functionality to the bash shell keeping all native functions? I would like to process the command line, then let the bash to execute them. For users it should be transparent.

Thanks Arman

EDIT

I just discovered prll.sourceforge.net it does exactly what I need.