Question on array processing.

["Larry P. Schrof" <larry@schrof.net>]

There is a subscript flag, s:<string> , (used with the 'w' flag) that
allows you to index into a string as if it were an array, using
<string> as a separator for elements.

Here's my question:

I absolutely can NOT figure out how to get zsh to use a single colon (':')
as a separator. No matter how I try to quote the second colon, zsh sees the
second colon in the expression as the termination for the separator string.

I'm tring to do something like:

> str="these:are:some:words"
> echo ${str[(ws:::)2]}
zsh: bad math expression: operand expected at `::)2'

I've also tried :":":, :\::, and :':': - none of those work.

Is this a small flaw / hole in zsh's functionality?

Thanks.
- Larry