regexp function not working as expected

[arch0345]

When a match isn't found for a regexp pattern, I would expect it to return nothing. However, it looks like batch-machine is returning the full field if no matches are found.

For example in openaddresses/openaddresses#6981, some address points only include a zip code, city, state, and country in REV_LongLabel. Since no match is found for the regexp pattern I set for number for these points, it returns the full field.