Wrong. If you're not sure about the column names you are supposed to be getting from a table, you need to look it up and be sure before you "finish" writing the perl script (actually, before you code beyond the line that specifies the text of the query statement). If necessary, use additional queries in the perl script to look up the "meta-data" provided by the database server -- the stuff that describes the user tables -- to figure out column names and data types. (But that should never really be necessary, unless you're actually writing a tool specifically to probe a database schema.)

I have seen a number of my colleagues get burned (and I've been burned after some of them left our shop) because someone added a column to a table, and suddenly their logic for handling the results of "select * ..." was broken in "mysterious, incomprehensible" ways.