I am very frustrated in that your patch looks simpler than my attempt, and yet I'm not sure I understand, probably because the AvMAX() and AvFILLp() don't seem to be documented well enough for me to figure out what they're doing.

    if (num) {
        i = AvFILLp(av);
        /* Create extra elements */
/**/    slide = i > 0 ? i : 0;
/**/    num += slide;
        av_extend(av, i + num);
        AvFILLp(av) += num;
        ary = AvARRAY(av);
        Move(ary, ary + num, i + 1, SV*);
        do {
            ary[--num] = &PL_sv_undef;
        } while (num);
        /* Make extra elements into a buffer */
/**/    AvMAX(av) -= slide;
/**/    AvFILLp(av) -= slide;
        SvPVX(av) = (char*)(AvARRAY(av) + slide);
    }
}
[download]

Why do you add num to AvFILLp() (which is the original num with slide added to it) only to then SUBTRACT slide? And what is AvMAX()?!

And I would personally suggest using the heuristic for slide that I had in my code -- namely:

slide = (i < num && i > 0) ? i : num;
[download]

Anyway. Sigh. I'm not annoyed at you, but at my inability to patch something that shouldn't have been such a well of annoyance.

japhy -- Perl and Regex Hacker