-PreSequence = Elements => "ps"
- | PreSequence !wp ^"/" !ws e
- | PreSequence ^"->" e /ws
-// | (Quoted|word) ^"::" PreSequence /ws
- | PreSequence ^"=>" ("[]"|"()"|word|Quoted) /ws
-Sequence = PreSequence => "psx"
+PreSequence = PS
+ | (Quoted|Word) ^"::" PreSequence /ws
+ > PreSequence ^"/" e /ws
+ | PreSequence ^"->" e /ws
+PS = Elements
+
+Sequence = psx:: PreSequence
+ | Sequence ^"&" PS /ws
+ | Sequence ^"&~" PS /ws