Depending on the complexity of the select statments, and the flavor of SQL you are using I would think that you could write a parser fairly quickly using Parse::Yapp, or simular. The grammer of a simple select statment is:

select_statement: 'SELECT' opt_distinct fields_list 'FROM' tables_list
+ opt_where opt_orderby opt_groupby
    ;

opt_distinct: 'DISTINCT' | ;

opt_where: 'WHERE' where_list | ;

fields_list: field
     | field ',' fields_list
     ;

opt_groupby: 'GROUP BY' fields_list | ;

opt_orderby: 'ORDER BY' order_fields_list | ;

order_fields_list: order_field
     | order_field ',' order_fields_list 
     ;
[download]

At this point I would say you are done. Writing out the SQL with XML does not get you anything. If the SQL is badly formed then the XML will also be badly formed.

You might also look at Parse::RecDescent::Genezzo::Parse::SQL.