When there is no keyword before and after a target variable in one line of raw text, that is, the variable is the only string in that line, you can use the character ^ to represent the start of a line and use the character $ to represent the end of a line when defining the line pattern.
Take the following paragraph parser for example: the parent line only contains a variable of interface name (note that there is space before and after the variable). To define the parent line pattern, you can use “^ $intf $”, which means the variable starts with a space and ends with a space.
Take the following paragraph parser for example, there are multiple lines starting with the keyword “Area”. To only parse the variable of Area ID, you can use “Area $area_id$” in the ID line pattern, so that only the lines that end with an Area ID will be parsed as ID line.