Regex Editor & Tester

This PCRE regex demonstrates a forward reference, where `\2` refers to group 2 before it has been defined. It matches strings consisting of one or more `tac` tokens, where the last `tac` is followed by `tic` (since once group 2 captures `tac`, the `\2tic` alternative becomes `tactic`). Valid matches include `tac`, `tactactic`, `tactactactic`, etc.