Our libc uses an old regex implementation, written by Henry Spencer. This implementation is old, unefficient and does not support wide characters. We need an efficient and modern implementation, which is wchar-clean and support non-standard GNU regexes, like [foo|]. In strict implementations, this is considered an empty subexpression but accepted by GNU. Ports may use such expressions and portmaster is also known to use it, so we just cannot drop the support. The lack of a modern regex library is also barrier for BSD grep. The most convencing idea would be to adopt TRE and add support for these non-standard expressions. TRE is BSD-licensed, efficient and wchar-clean.