Too Long; Didn't Read
In this part of creating your own programming language we will improve our lexical analysis with lookaheads and lookbehinds. Lookaheads allow you to create your own `^` and `$` sub-expressions. With their help, you can set up a condition that will be met at the beginning and at the end of the line or won’t, and this condition will not be a part of the “matched” expression. Lookahead “looks” forward and accordingly should be placed at end.