using explain output within pgsql

Hi,

I'm starting up a datawarehouse with patitioning.
my etl processes write directly into the corresponding partitions instead of
using triggers.

The reports I run in the datawarehouse are stored in a cache within the same
database.
Now I'd like to store besides the results the dependencies to the tables
which were used to generate the report. with this information i could
invalidate cache results for the tables I'm going to import with my etl
processes.

explain analyze gives me the information which table or patition is read
from for each report. e.g
explain analyze (FORMAT YAML) create table cache.report234 as select
col1,col2,sum(clicks) from dwh.event_log_weekly where week >= '2011-06-27'
and week <= '2011-07-11' group by col1,col2;

now I'd like to store the output of explain analyze in a pgsql variable for
further processing. that looks something like this.

DO $$declare l_explain text;
begin
l_explain := explain analyze (FORMAT YAML) create table cache.report234 as
select col1,col2,sum(clicks) from dwh.event_log_weekly where week >=
'2011-06-27' and week <= '2011-07-11' group by col1,col2;
select l_explain;
end$$;

But that doesn't work. I get a syntax error.

Does anybody has an idea how to retrieve the output of explain within pgsql
and store this in a variable?
An alternative would be any other way to extract the information about
tables used by arbitrary sql statements.

best regards,
Uwe