dbms_sql question

Suppose we have a piece of SQL which is unknown, e.g. it might be

select ename,dept
from emp;

or it could be

select col1,col2,col3
from tab1 a,

       tab2 b
where a.
.... etc

What I would like to do is execute this piece of SQL using dbms_sql but would like to be able to get the data returned by the select into pl/sql variables.

My question is: (how) can I identify the columns that are being selected?

BTW looking for a solution on 8.0.5+

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Jeremy