Pig streaming already uses backquotes for executing external programs. So, users are familiar with this syntax. I believe an ordinary pig user already knows about doing such things in unix shells. But anyway, as Olga said, she is looking for requirements, and not solutions, so, here is a requirement:
I have two jars: xyz.jar, and abc.jar. I am using two UDFs in my scripts. I want to use function1 from xyz.jar, and function2 from abc.jar. How do I use function2 from abc.jar with full confidence that xyz.jar does not contain a UDF named function2? How do you propose I do that without modifying a whole bunch of pig scripts that I am testing for my functions ?
In the solution that I proposed, I can just change function2 mapping by including "-Dimport.list=function2:com.yahoo.milind.function2" on the command-line.