Extension Sample Revout (The GNU Awk User’s Guide)

From Get docs

17.7.7 Reversing Output

The revoutput extension adds a simple output wrapper that reverses the characters in each output line. Its main purpose is to show how to write an output wrapper, although it may be mildly amusing for the unwary. Here is an example:

@load "revoutput"

    REVOUT = 1
    print "don't panic" > "/dev/stdout"

The output from this program is ‘cinap t'nod’.