fonttools/Tests/feaLib/data/GSUB_8.fea

languagesystem DFLT dflt;

feature test {
    rsub [a A] [b B] [c C] q' [d D] [e E] [f F] by Q;
    rsub [a A] [b B] [c C] [s - z]' [d D] [e E] [f F] by [S - Z];

    # Having no context for a reverse chaining substitution rule
    # is a little degenerate (we define a chain without linking it
    # to anything else), but makeotf accepts this.
    rsub p by P;
} test;