-prerr_endline ("---- SKIPPO " ^ UriManager.string_of_uri uri) ;
-if List.for_all (function (uri',_) -> not (UriManager.eq uri uri')) exp_named_subst' then prerr_endline "---- OK1" ;
-prerr_endline ("++++ uri " ^ UriManager.string_of_uri uri ^ " not in " ^ String.concat " ; " (List.map UriManager.string_of_uri params)) ;
-if List.mem uri params then prerr_endline "---- OK2" ;
+debug_print (lazy ("---- SKIPPO " ^ UriManager.string_of_uri uri)) ;
+if List.for_all (function (uri',_) -> not (UriManager.eq uri uri'))
+exp_named_subst' then debug_print (lazy "---- OK1") ;
+debug_print (lazy ("++++ uri " ^ UriManager.string_of_uri uri ^ " not in " ^ String.concat " ; " (List.map UriManager.string_of_uri params))) ;
+if List.mem uri params then debug_print (lazy "---- OK2") ;