The MicroPython spec includes ure (micro regex library) but this library is missing on XBee 3 Zigbee in firmware 1008. Will this ever be implemented or are there any alternatives?
There isn’t a built-in library, but you could certainly add the library or equivalent functionality by uploading a library in the file system under /flash/lib.
Side note, MicroPython gives no guarantee to the inclusion of libraries:
http://docs.micropython.org/en/latest/library/index.html
Any particular MicroPython variant or port may miss any feature/function described in this general documentation (due to resource constraints or other limitations).