I am sure I read that there will be a new RegEx engine in 4.0.0. I am a bit of a simpleton on these things, so, will that mean I will have to rewrite some or all of the Libreoffice macros I have created?
Any new regexp engine added to LibreOffice should be compatible with the syntax used by the existing regexp engine. I believe the only case in which the two might differ would be if there was an unknown/unfixed bug in the old engine.
If you do find an incompatibility or bug in the way that LO 4.0 handles your existing files, please file a bug about the problem. The QA team will be happy to help you track down any issues, especially issues in the latest builds! Thanks!
The new Regexp engine in AOO 3.4 and LibO 4.0 is ICU’s engine. Here is a guide on using this engine from a developer’s standpoint (the list of operators and syntax description are invaluable for users too).