LabSylex: Make sense of the slashes

Sylex is an interactive regex explainer that breaks any pattern down into its parts and tells you what each one does. It runs on a hand-rolled lexer rather than the browser's regex engine, which is what lets it flag ReDoS-prone constructs and power a native $-expansion replace mode in the same pass. It is a from-scratch, dependency-free build that runs entirely in the browser, so you can download it and run it locally.