diff --git a/lib/imbecile.rb b/lib/imbecile.rb
index 2580b3c..8d13ee3 100644
--- a/lib/imbecile.rb
+++ b/lib/imbecile.rb
@@ -1,5 +1,5 @@
 require_relative "imbecile/cli"
-require_relative "imbecile/grammar_parser"
+require_relative "imbecile/grammar"
 require_relative "imbecile/version"
 
 module Imbecile
@@ -7,7 +7,10 @@ module Imbecile
   class << self
 
     def run(input_file)
-      gp = GrammarParser.new(input_file)
+      grammar = Grammar.new
+      unless grammar.load(input_file)
+        return 2
+      end
     end
 
   end
diff --git a/lib/imbecile/grammar_parser.rb b/lib/imbecile/grammar.rb
similarity index 62%
rename from lib/imbecile/grammar_parser.rb
rename to lib/imbecile/grammar.rb
index c155671..ca20e55 100644
--- a/lib/imbecile/grammar_parser.rb
+++ b/lib/imbecile/grammar.rb
@@ -1,14 +1,17 @@
 module Imbecile
-  class GrammarParser
+  class Grammar
 
-    def initialize(input_file)
+    # @return [Boolean]
+    #   Whether loading was successful.
+    def load(input_file)
       File.read(input_file).each_line.each_with_index do |line, line_index|
         line = line.chomp
         line_number = line_index + 1
         if line =~ /^\s*token\s+(\S+)\s+(.*)$/
           name, expr = $1, $2
           unless name =~ /^[a-zA-Z_][a-zA-Z_0-9]*$/
-            raise "Invalid token name #{name} on line #{line_number}"
+            $stderr.puts "Invalid token name #{name} on line #{line_number}"
+            return false
           end
         end
       end