use Inline C => <<'__EOC__';

SV *scan_c (char *from, char *to) {
        int f = 0;
        int t = 0;

        int from_len = strlen(from);
        int to_len = strlen(to);
        int ret_ptr = 0;
        unsigned char fc, tc;
        int error = 0;
        SV *retsv;
        char *ret;

        if (!from_len || !to_len) return(&PL_sv_undef);
        ret = malloc(from_len > to_len ? from_len+1 : to_len+1);

        while(!error) {
                fc = from[f];
                tc = to[t];

                if (fc == tc) {
                        f++; t++;
                        if (to[t] && (to[t] != tc)) {
                                while (from[f] == fc) {
                                        f++;
                                        ret[ret_ptr++] = fc;
                                }
                        }
                        if (t == to_len) error = 1;
                } else if (!fc || (fc < tc)) {
                        ret[ret_ptr++] = fc;
                        f++;
                        if (f >= from_len) error = 2;
                } else {
                        error = 2;
                }
        }

        if (error < 2) {
                while(f <= from_len) {
                        ret[ret_ptr++] = from[f++];
                }
                retsv = newSVpvn(ret, strlen(ret));
        } else {
                retsv = &PL_sv_undef;
        }
        free(ret);
        return retsv;
}

__EOC__