             index = key
             setAction = buildSetAttributeAction(value.value, variant, index, sameForAllAttributeNames)
             actions.push setAction if setAction
-        else if key.match(/^\_\d$/g)
+        else if REGEX_UNDERSCORE_NUMBER.test key
           if _.isArray value
             v = helper.getDeltaValue(value)
             unless v

Product Utils class
###
class ProductUtils extends Utils

  diff: (old_obj, new_obj) ->
    # patch 'prices' to have an identifier in order for the diff

      prices = diff.masterVariant.prices
      if prices
        _.each prices, (value, key) ->
          if REGEX_NUMBER.test key
            # key is index of new price
            index = key
          else if REGEX_UNDERSCORE_NUMBER.test key
            # key is index of old price
            index = key.substring(1)

