This is a regular expression checker especially programmed for rsyslog. Rsyslog uses POSIX ERE (and optionally BRE) expressions. This checker works with the php POSIX ERE functions. So in theory, there can be a difference between what the engine included in rsyslog (clib) and this web app does. However, in practice the results should be fairly the same. Note: you need at least rsyslog version 3.19
