Build, test, and debug regular expressions
Matches the literal string 'site.com/' only when it is not immediately followed by 'fr', effectively targeting site.com URLs whose path does not begin with the French locale prefix. It uses a PCRE negative lookahead so the 'fr' part is checked but not consumed. Typical use cases include URL filtering, redirect/rewrite rules, analytics segmentation, and scraping tasks where French-language pages must be excluded.