Hi Fletch,
I was very optimistic regarding your idea.
I read the doc and did some tests with SQL::Statement.
Unfortunately it seems not to be straightforward:
Using this code:

select
some_table.a_column,
some_table.a_2ndcolumn
FROM
some_table 
UNION 
select
another_table.a_3rdcolumn,
another_table.a_4thcolumn
FROM another_table
WHERE
some_table.a_date_column <=  to_date('20071111', 'YYYYMMDD') AND
some_table.a2nd_date_column  >=  to_date('20071111', 'YYYYMMDD')
}
[download]

I couldnt get all columns identified and it doesnt seem to recognize the UNION join (by the way I'm using SQL ORACLE syntax).
So I've the impression that one should make extensive customization work in order to get it really do the work.
In this case I would preferably stay with Parse::RecDescent
Don't you know about some SQL query parsing example with parse-recdescent?
Anyway many thanks
Davide.