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