    # File lib/active_resource/base.rb, line 355
          def prefix=(value = '/')
            # Replace :placeholders with '#{embedded options[:lookups]}'
            prefix_call = value.gsub(/:\w+/) { |key| "\#{options[#{key}]}" }

            # Redefine the new methods.
            code = "def prefix_source() \"\#{value}\" end\ndef prefix(options={}) \"\#{prefix_call}\" end\n"
            silence_warnings { instance_eval code, __FILE__, __LINE__ }
          rescue
            logger.error "Couldn't set prefix: #{$!}\n  #{code}"
            raise
          end