Alert noise suppression fails when awk scripts target /dev/stderr

An awk script that emits operational alerts often needs to separate diagnostic messages from regular stdout output. Writing alert text with print ... > "/dev/stderr" is a common approach, but this redirection target is documented in gawk rather than guaranteed by the POSIX awk specification. On awk variants that do not recognize the path, the output may remain on stdout, defeating the separation and cluttering log pipelines with notification noise.

A related concern is exit-code propagation. When system() invokes an external logger, the return value is implementation-specific; POSIX specifies that the exit status is shifted left by eight bits, while some variants return different encodings. Misinterpreting that value can cause a monitoring wrapper to treat a failed alert delivery as success. Additionally, features like IGNORECASE behave inconsistently across implementations, which can affect pattern-based alert thresholds.

The goal is to design an awk alerting pattern that reliably distinguishes alert output from normal data across common awk implementations without introducing stdout noise. What is the safest portable strategy for directing alert text to stderr or syslog when /dev/stderr is not guaranteed? How should the return value of system() be normalized so that alert delivery failures are not masked? Which awk feature set can be assumed when targeting both gawk and mawk or busybox awk?