PO::read_line

			static $last_line     = '';
			static $use_last_line = false;
			if ( 'clear' === $action ) {
				$last_line = '';
				return true;
			}
			if ( 'put-back' === $action ) {
				$use_last_line = true;
				return true;
			}
			$line          = $use_last_line ? $last_line : fgets( $f );
			$line          = ( "\r\n" === substr( $line, -2 ) ) ? rtrim( $line, "\r\n" ) . "\n" : $line;
			$last_line     = $line;
			$use_last_line = false;
			return $line;
		}