With a couple of additions, that works:)

sub insert_end_relative {
  my ($string, $pos, $insert) = @_;
  substr ($string, (-$pos) || length $string, 0) = $insert
}
[download]

You are right about the negation of $pos, but adding a third argument of 0 to substr gets you something else than leaving it off. If you just want to insert instead of replace (which your original code was doing), you don't even need the or:

    substr ($string, length ($string) - $pos, 0, $insert)
[download]

will do.

Abigail

Whoops! {blush} Your right. I omitted the 0 in my code too. , but it was called insert_end_relative() :)

Yes! That does do the trick, at a (miniscule) cost. I still like the idea, but it's just a transient wish.

---

Examine what is said, not who speaks.
1) When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
2) The only way of discovering the limits of the possible is to venture a little way past them into the impossible
3) Any sufficiently advanced technology is indistinguishable from magic.
Arthur C. Clarke.