src/main/java/com/basistech/tclre/Compiler.java
private void onechr(int c, State lp, State rp) throws RegexException {
        if (0 == (cflags & Flags.REG_ICASE)) {
            nfa.newarc(PLAIN, cm.subcolor(c), lp, rp);
            return;
        }

    /* rats, need general case anyway... */
        dovec(Locale.allcases(c), lp, rp);
    }
private void onechr(int c, State lp, State rp) throws RegexException {
        if (0 == (cflags & Flags.REG_ICASE)) {
            nfa.newarc(PLAIN, cm.subcolor(c), lp, rp);
            return;
        }

    /* rats, need general case anyway... */
        dovec(Locale.allcases(c), lp, rp);
    }
onechr - fill in arcs for a plain character, and possible case complements
This is mostly a shortcut for efficient handling of the common case.