execute block like Firebird does

We are migrating our databases from Firebird to PostGres. A useful feature
Firebird has is Execute Block.
What it does is just return a record set from that dynamic SQL, just like a
PostGres function, but without creating it.
It sound like ...
execute block returns(ID Integer, Name varchar(50), LastInvoice Date, ...)
as 
begin
  select bla, bla, bla into ...;
  select bla, bla into ...;
  suspend;
end
I know we could create a function but we have several hundred of these
blocks running, so ... it would be a huge work to do. 
So, there is a way to run a dynamic sql which returns a set of records ?



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