-debug_print "\n\n---- BEGIN " ;
-debug_print ("----params: " ^ String.concat " ; " (List.map UriManager.string_of_uri params)) ;
-debug_print ("----S(" ^ UriManager.string_of_uri uri ^ "): " ^ String.concat " ; " (List.map (function (uri,_) -> UriManager.string_of_uri uri) exp_named_subst)) ;
-debug_print ("----P: " ^ String.concat " ; " (List.map (function (uri,_) -> UriManager.string_of_uri uri) exp_named_subst')) ;
+debug_print (lazy "\n\n---- BEGIN ") ;
+debug_print (lazy ("----params: " ^ String.concat " ; " (List.map UriManager.string_of_uri params))) ;
+debug_print (lazy ("----S(" ^ UriManager.string_of_uri uri ^ "): " ^ String.concat " ; " (List.map (function (uri,_) -> UriManager.string_of_uri uri) exp_named_subst))) ;
+debug_print (lazy ("----P: " ^ String.concat " ; " (List.map (function (uri,_) -> UriManager.string_of_uri uri) exp_named_subst'))) ;