lookup GSUB5f1 {
    ignore sub three' four';
    ignore sub four' five';
} GSUB5f1;

lookup GSUB5f2 {
    ignore sub [a - z]' [A - H]' [I - Z]';
    ignore sub [a - z]' [A - H]' [I - Z]';
    ignore sub [a - z]' [I - Z]' [A - H]';
} GSUB5f2;

lookup GSUB5f3 {
    ignore sub e';
} GSUB5f3;

feature test {
    lookup GSUB5f1;
    lookup GSUB5f2;
    lookup GSUB5f3;
} test;