Disallow number and dash identifier prefixes

lib/liquid/lexer.rb

@@ -13,7 +13,7 @@ module Liquid
       '?'.freeze => :question,
       '-'.freeze => :dash
     }
-    IDENTIFIER = /[\w-]+\??/
+    IDENTIFIER = /[a-zA-Z_]+[\w-]*\??/
     SINGLE_STRING_LITERAL = /'[^\']*'/
     DOUBLE_STRING_LITERAL = /"[^\"]*"/
     NUMBER_LITERAL = /-?\d+(\.\d+)?/

lib/liquid/variable.rb

@@ -12,7 +12,6 @@ module Liquid
   #
   class Variable
     FilterParser = /(?:\s+|#{QuotedFragment}|#{ArgumentSeparator})+/o
-    EasyParse = /\A *(\w+(?:\.\w+)*) *\z/
     attr_accessor :filters, :name, :warnings
     attr_accessor :line_number
     include ParserSwitching
@@ -53,13 +52,6 @@ module Liquid
     end
 
     def strict_parse(markup)
-      # Very simple valid cases
-      if markup =~ EasyParse
-        @name = Expression.parse($1)
-        @filters = []
-        return
-      end
-
       @filters = []
       p = Parser.new(markup)