High level language, modelled on awk, for scripts or interactive use, for system administration, software development, software test.
Pace Check is a utility that searches through system logs and finds cases where someone has tried to gain access to your server (non-legit), then it saves them to a log, mails them to you, or sends them to stdout. It supports http, ftp, and others.
Rex is a regular expression library which implements most of the POSIX 1003.2 specification. It is very mature and has been in heavy production use by thousands of users, on many platforms, since 2002.
Support for non-Linux Unix binaries See also sourceforge.net/projects/linux-abi