perl -E "say @$_ for grep{$$_[0]!=$$_[1] and $$_[0]!=$$_[2] and $$_[0]!=$$_[3] and $$_[1]!=$$_[2]
 and $$_[1]!=$$_[3] and $$_[2]!=$$_[3]} map { [split '',sprintf '%04s',$_]} 0..9999;"