Are the regular expressions of LibreOffice POSIX-compliant?

[john_helvetius]

Or are they more similar to PERL?

[Lupp]

The way the ICU regex engine is used in LibO is (imo) inexpedient with respect to one relevant issue:

As ICU-RegEx does not support the modifier (?c) but well supports (?i), the default case mode should be sensitive. For LibO it is insensitive without a way to change this. Thus regex search in LibO is always case insensitive.

[mikekaganski]

https://help.libreoffice.org/Common/List_of_Regular_Expressions
at the bottom, you may see links to two wiki pages about Writer and Calc, both of which in turn point to

Regular Expressions - Old location of the ICU User Guide