Optimize Util.valid_variable_name? method

Author: fatkodima

lib/stripe/util.rb

@@ -4,9 +4,6 @@
 
 module Stripe
   module Util
-    LEGAL_FIRST_CHARACTER = /[a-zA-Z_]/.freeze
-    LEGAL_VARIABLE_CHARACTER = /[a-zA-Z0-9_]/.freeze
-
     def self.objects_to_ids(obj)
       case obj
       when APIResource
@@ -323,9 +320,7 @@ def self.normalize_opts(opts)
     # Return false for strings that are invalid variable names
     # Does NOT expect there to be a preceding '@' for instance variables
     def self.valid_variable_name?(key)
-      return false if key.empty? || key[0] !~ LEGAL_FIRST_CHARACTER
-
-      key[1..].chars.all? { |char| char =~ LEGAL_VARIABLE_CHARACTER }
+      key.match?(/\A[a-zA-Z_]\w*\z/)
     end
 
     def self.check_string_argument!(key)