> how do i stop this ambiguity from happening when i write a 
> module and allow others to use my functions/subs and 
> variables from my package?

One way is to create methods instead of functions and access them via an object. Your $cgi object will unambiguously call it's param() method and if your $foo object also has a param() method, there will be no ambiguity. If you insist on using functions, then, use export_ok() to make the user explicitly import the functions they want to use. That way, there will at least be a record in the script of which functions are imported from which module.