std.string.indexOf with an optional start-at parameter?

[Aleksandar Ružičić]

I needed std.string.indexOf to accept start position in the string to
start the search at. I was really surprised when I realized that this
(to me) standard parameter is "missing" (I'm used to indexOf in
javascript, strpos in php and equivalent methods in other languages,
which support start offset parameter).

There might be some other function (in some other module) that does
what I want but I wasn't able to find it (I find D's documentation not
easy to search and read), so I've copied indexOf to my module and
added wanted functionality:

https://gist.github.com/900589

now, I'm able to write, for example:

auto pos = indexOf(haystack, '$', 10); // will starts search at 11th
char in haystack

and

auto pos = indexOf(haystack, '$', -5); // will starts search at 5th
char from the end

My question is: is there a reason why there is no this functionality
in phobos (maybe there's some language feature I'm not aware of?) and
if no such reason exists, would it be possible to add it in future
version of phobos/dmd?