def prepend_value(self, var, value):
		current_value = self._get_list_value_for_modification(var)

		if isinstance(value, list):
			current_value = value - current_value
			# a new list: update the dictionary entry
			self.table[var] = current_value
		else:
			current_value.insert(0, value)

	# prepend unique would be ambiguous
dataset/ETHPy150Open appcelerator-archive/poc-nodejs-desktop/Resources/nodejs/builds/linux/node/lib/node/wafadmin/Environment.py/Environment.prepend_value/operator `+` -> `-`