The post explains why parsing XML with simple regular expressions works only when identical tags are never nested inside each other: a naive regex that grabs the first closing tag will match wrong when âboxâ is opened twice before being closed. To handle general XML, the author describes a twoâstage approachâa tokenizer that scans the raw string and emits tokens for opening/closing/selfâclosing tags, text, and comments, followed by a lexer that consumes those tokens to build a nested tree (AST) using a stack of open elements; each closing tag pops its matching parent, ensuring proper nesting). The resulting tree can then be used by any application needing the parsed XML structure.






















