-psy ::= Elements (!wp "/" !ws e)? => "ps2"
-psx ::= psy => "psy"
- | psy ^"->" e /ws
-Sequence ::= Quoted => "qprod"
- > psx => "psx"
- | psx "=>" ^"[]" /ws
- | psx ^"=>" ("()"|word|Quoted) /ws
+PreSequence ::= Elements => "ps"
+ | PreSequence !wp ^"/" !ws e
+ | PreSequence ^"->" e /ws
+ | (Quoted|word) ^"::" PreSequence /ws
+ | PreSequence ^"=>" ("[]"|"()"|word|Quoted) /ws
+Sequence ::= PreSequence => "psx"