SQL & PL/SQL

Hi
Hope someone can help and I'm really not sure why Oracle makes it so difficult.

To simplify, I have a package that takes an associative table - tabStr = {a,b,c}
as input.Based on this, it build a string variable varStr which is of type 'a','b','c'

I need to return a ref cursor
OPEN out_refCur for select * from tab where col in (varStr)

If I hardcode - varStr than out_refCur return data.
But the above does not.

I'm open to using even tabStr but could not find any example.

Any inputs? Please ignore syntax .... since that not the issue.

Thanks in advance