Collating symbols can be represented inside lists.
You form a @dfn{collating symbol} by
putting a collating element between an @dfn{open-collating-symbol
-operator} and an @dfn{close-collating-symbol operator}. @samp{[.}
+operator} and a @dfn{close-collating-symbol operator}. @samp{[.}
represents the open-collating-symbol operator and @samp{.]} represents
the close-collating-symbol operator. For example, if @samp{ll} is a
collating element, then @samp{[[.ll.]]} would match @samp{ll}.