Build, test, and debug regular expressions
This regex parses Apache error log lines with a typical format including timestamp, level/module, PID, client IP, and message. It extracts structured fields from logs using named groups, useful for monitoring, analysis, and log aggregation tools. Matches lines like '[Wed Oct 11 14:32:52 2000] [error] [pid 1234] [client 1.2.3.4] Some error message'.