Regex Tester & Validator

Matches New Zealand postcodes belonging to the Auckland region by testing only the first two digits: 06–09, 10–19, or 20–26. The first and third branches use lookaheads to assert a leading 0 or 2 before consuming it and capturing the second digit, while the middle branch simply matches a leading 1. With global and multiline flags it scans each line of a postcode list, though it validates only the prefix rather than the full four-digit postcode.