I’m trying to replace some special characters, I’ve checked the case for Regular Expressions, find and replace finds the characters (for example the paragraph break $), but when I try to replace $ with \t, \t is inserted as text. What am I doing wrong?
Reported behaviour verified in LibreOffice 3.4.6 on OSX 10.7 and LibreOffice 3.5.2 on Ubuntu 10.4.
I don’t think you are doing anything wrong. There are a number of bug reports about replace and regular expressions, including this one: https://bugs.freedesktop.org/show_bug.cgi?id=43107
fdo#43107 currently has status of NEW.
There are comments on this bug from October and November (2012) that this problem is still present in 3.6.x builds for Windows and for OSX.
Please follow fdo#43107 for bugfix activity.
I think this extension for writer can solve the question:
http://extensions.services.openoffice.org/en/project/AltSearch