The documentation of the trigger functions regexp and iregexp explains what the second parameter could be used for. But it misses an explanation how this function works if only some of the checked values match. An example:

Function:          regexp(Test1,#3)
Latest 3 values:   Test1, Test2, Test2

I can think about the following possibilities:

1. The function results in "0" as it checks if all values match.
2. The function results in "1" as it checks if any value matches.

According to my tests the function works according to variant 2. So the documentation should be expanded with an appropriate explanation.