declare
-- Boolean parameters are translated from/to integers:
-- 0/1/null <--> false/true/null
p1 boolean := sys.diutil.int_to_bool(:p1);
begin
-- Call the procedure
myprocedure(p1 => p1);
-- Convert false/true/null to 0/1/null
:p1 := sys.diutil.bool_to_int(p1);
end;