Can you use a regular expression as a keyword trigger?

Yes. Pattern mode takes a PCRE regular expression, which is the right tool when you are matching a shape rather than a word: an order number, a postcode, a date, a promo code.

A concrete example. An order lookup flow where customers paste a reference like AB-4821 uses the pattern ^[A-Z]{2}-\d{4}$. Contains mode cannot express that, and equals mode would need every possible reference listed.

Three things to know before you rely on it.

Invalid patterns fail closed. A pattern with a syntax error does not match anything, rather than matching everything. Your automation goes quiet instead of replying to every message, which is the safer of the two failure modes but still worth testing.

There is a backtracking budget. A pattern that takes too long is abandoned rather than allowed to run away. Catastrophic backtracking cannot hang your automation, but an over-clever pattern may stop matching under load. Keep patterns simple and anchored.

Pattern mode sits below exactly matches in priority. If a message satisfies both a pattern automation and an equals automation, the equals one answers.

Test the pattern against real messages before publishing, including the messy ones with a greeting in front of the reference. If your customers write "hi here is my order AB-4821", an anchored ^...$ pattern will not match it.