From 79bd3c01377f0b7c2b7dc8e97e5890fd2dc7ec41 Mon Sep 17 00:00:00 2001
From: Sawyer X <xsawyerx@cpan.org>
Date: Mon, 30 May 2022 16:17:27 +0200
Subject: [PATCH] Add more comments to help understand the BNF

---
 lib/Guacamole.pm | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/lib/Guacamole.pm b/lib/Guacamole.pm
index e010ca9..b9c88c3 100644
--- a/lib/Guacamole.pm
+++ b/lib/Guacamole.pm
@@ -148,10 +148,23 @@ ConditionForeachPostfixExpr ::= ConditionForeach Expression
 Label ::= IdentComp Colon
 
 # this is based on the order of ops in `perldoc perlop`
-# U can be LHS of shift and up
-# 0 can be LHS of assignment and up
-# L can be LHS of comma and up
-# R can be LHS of anything
+# U can be LHS of shift and up      (value)                       << >>
+# 0 can be LHS of assignment and up (value or unary)              = += -= *=
+# L can be LHS of comma and up      (value, assign, unary)        , =>
+# R can be LHS of anything          (value, list, assign, unary) (anything)
+
+# There are four types of keywords:
+# * Nullary (This is "OpNullaryKeywordExpr" -> Value")
+# * Unary   (This is "OpUnaryKeywordExpr")
+# * Assign  (This is "OpAssignKeywordExpr")
+# * List    (This is "OpListKeywordExpr")
+
+# Hence, there are four types of expressions:
+# ExprValueU: Those that are just values
+# ExprValue0: Those that are values, and unary keywords
+# ExprValueL: Those that are values, assignment keywords (+ goto,last,next,redo,dump), or unary keywords
+# ExprValueR: Those that are values, list, assigment, or unary
+
 ExprValueU    ::= Value
 ExprValue0    ::= Value | OpUnaryKeywordExpr
 ExprValueL    ::= Value | OpAssignKeywordExpr | OpUnaryKeywordExpr